title: Why does [NSTextStorage setAttributedString] crash with NSMutableAttributedString?
body: <p>When I run the following Code it crashes at the last line. I don't have any idea why. This function gets called in awakeFromNib.</p>
  
  <pre><code>- (void)setMotdText:(NSString *)text
  {
      NSString *boldFontName = [[NSFont boldSystemFontOfSize:12] fontName];
      NSMutableAttributedString *attrstr = [[NSMutableAttributedString alloc] initWithString:text];
  
      [attrstr beginEditing];
  
      [attrstr addAttribute:NSFontAttributeName value:boldFontName range:NSMakeRange(0, 16)];
  
      [attrstr endEditing];
  
      [self.motdTextView.textStorage setAttributedString:attrstr];
  }
  </code></pre>
  
  <p>I get this crash log:</p>
  
  <pre><code>2012-06-22 11:32:22.348 MSM-Plan[20785:403] -[__NSCFConstantString _isDefaultFace]: unrecognized selector sent to instance 0x7fff79b9f380
  2012-06-22 11:32:22.349 MSM-Plan[20785:403] An uncaught exception was raised
  2012-06-22 11:32:22.349 MSM-Plan[20785:403] -[__NSCFConstantString _isDefaultFace]: unrecognized selector sent to instance 0x7fff79b9f380
  2012-06-22 11:32:22.351 MSM-Plan[20785:403] (
      0   CoreFoundation                      0x00007fff8a5bef56 __exceptionPreprocess + 198
      1   libobjc.A.dylib                     0x00007fff8ae19d5e objc_exception_throw + 43
      2   CoreFoundation                      0x00007fff8a64b1be -[NSObject doesNotRecognizeSelector:] + 190
      3   CoreFoundation                      0x00007fff8a5abe23 ___forwarding___ + 371
      4   CoreFoundation                      0x00007fff8a5abc38 _CF_forwarding_prep_0 + 232
      5   AppKit                              0x00007fff8e0b060c -[NSMutableAttributedString(NSMutableAttributedStringKitAdditions) fixFontAttributeInRange:] + 1249
      6   AppKit                              0x00007fff8e0afeb7 -[NSMutableAttributedString(NSMutableAttributedStringKitAdditions) fixAttributesInRange:] + 64
      7   AppKit                              0x00007fff8e19b521 -[NSTextStorage processEditing] + 107
      8   AppKit                              0x00007fff8e0c2564 -[NSTextStorage edited:range:changeInLength:] + 385
      9   Foundation                          0x00007fff8d6f4497 -[NSConcreteMutableAttributedString replaceCharactersInRange:withAttributedString:] + 328
      10  AppKit                              0x00007fff8e1dfd19 -[NSConcreteTextStorage replaceCharactersInRange:withAttributedString:] + 81
      11  MSM-Plan                            0x000000010206af5a -[MSM_PlanAppDelegate setMotdText:] + 314
      12  MSM-Plan                            0x000000010206c455 -[MSM_PlanAppDelegate awakeFromNib] + 1701
      13  CoreFoundation                      0x00007fff8a5b5fb1 -[NSObject performSelector:] + 49
      14  CoreFoundation                      0x00007fff8a5b5f32 -[NSSet makeObjectsPerformSelector:] + 274
      15  AppKit                              0x00007fff8e0369ff -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] + 1245
      16  AppKit                              0x00007fff8e02cf73 loadNib + 322
      17  AppKit                              0x00007fff8e02c470 +[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:] + 217
      18  AppKit                              0x00007fff8e02c38b +[NSBundle(NSNibLoading) loadNibFile:externalNameTable:withZone:] + 141
      19  AppKit                              0x00007fff8e02c2ce +[NSBundle(NSNibLoading) loadNibNamed:owner:] + 364
      20  AppKit                              0x00007fff8e29d06f NSApplicationMain + 398
      21  MSM-Plan                            0x000000010206adf2 main + 34
      22  MSM-Plan                            0x000000010206adc4 start + 52
  )
  2012-06-22 11:32:22.416 MSM-Plan[20785:403] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFConstantString _isDefaultFace]: unrecognized selector sent to instance 0x7fff79b9f380'
  *** First throw call stack:
  (
      0   CoreFoundation                      0x00007fff8a5bef56 __exceptionPreprocess + 198
      1   libobjc.A.dylib                     0x00007fff8ae19d5e objc_exception_throw + 43
      2   CoreFoundation                      0x00007fff8a64b1be -[NSObject doesNotRecognizeSelector:] + 190
      3   CoreFoundation                      0x00007fff8a5abe23 ___forwarding___ + 371
      4   CoreFoundation                      0x00007fff8a5abc38 _CF_forwarding_prep_0 + 232
      5   AppKit                              0x00007fff8e0b060c -[NSMutableAttributedString(NSMutableAttributedStringKitAdditions) fixFontAttributeInRange:] + 1249
      6   AppKit                              0x00007fff8e0afeb7 -[NSMutableAttributedString(NSMutableAttributedStringKitAdditions) fixAttributesInRange:] + 64
      7   AppKit                              0x00007fff8e19b521 -[NSTextStorage processEditing] + 107
      8   AppKit                              0x00007fff8e0c2564 -[NSTextStorage edited:range:changeInLength:] + 385
      9   Foundation                          0x00007fff8d6f4497 -[NSConcreteMutableAttributedString replaceCharactersInRange:withAttributedString:] + 328
      10  AppKit                              0x00007fff8e1dfd19 -[NSConcreteTextStorage replaceCharactersInRange:withAttributedString:] + 81
      11  MSM-Plan                            0x000000010206af5a -[MSM_PlanAppDelegate setMotdText:] + 314
      12  MSM-Plan                            0x000000010206c455 -[MSM_PlanAppDelegate awakeFromNib] + 1701
      13  CoreFoundation                      0x00007fff8a5b5fb1 -[NSObject performSelector:] + 49
      14  CoreFoundation                      0x00007fff8a5b5f32 -[NSSet makeObjectsPerformSelector:] + 274
      15  AppKit                              0x00007fff8e0369ff -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] + 1245
      16  AppKit                              0x00007fff8e02cf73 loadNib + 322
      17  AppKit                              0x00007fff8e02c470 +[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:] + 217
      18  AppKit                              0x00007fff8e02c38b +[NSBundle(NSNibLoading) loadNibFile:externalNameTable:withZone:] + 141
      19  AppKit                              0x00007fff8e02c2ce +[NSBundle(NSNibLoading) loadNibNamed:owner:] + 364
      20  AppKit                              0x00007fff8e29d06f NSApplicationMain + 398
      21  MSM-Plan                            0x000000010206adf2 main + 34
      22  MSM-Plan                            0x000000010206adc4 start + 52
  )
  terminate called throwing an exception(lldb)
  </code></pre>
  
  <p>Has anybody an idea? If I call it with a NSAttributedString-Object there´s no error.</p>