It’s hard work printing nothing
<i>There’s an argument to be made that silly error messages are better than crashing browsers</i><p>There's an argument, but it's a really lousy one.  If you're passing NULL as a string to printf, <i>your code is broken</i>.  A crash which results in someone tracking down and fixing the bug is far better than <i>quietly doing something which is 100% guaranteed to be wrong</i>.