Bug 75711 AstProvider should not create AST if requested by SelectionListenerWithASTManager
3.1 M2 If SelectionListenerWithASTManager waits for an AST and the editor closes we should not create an AST for that one but return null instead.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
try {
				type= TextUtilities.getContentType(document, IJavaPartitions.JAVA_PARTITIONING, offset, true);
			} catch (BadLocationException exception) {
				
			}
			
			int index= super.getLineStartPosition(document, line, length, offset);
			if (type.equals(IJavaPartitions.JAVA_DOC) || type.equals(IJavaPartitions.JAVA_MULTI_LINE_COMMENT)) {
				if (index < length - 1 && line.charAt(index) == '*' && line.charAt(index + 1) != '/') {
					do {
						++index;
					} while (index < length && Character.isWhitespace(line.charAt(index)));
				}
			} else {
				if (index < length - 1 && line.charAt(index) == '/' && line.charAt(index + 1) == '/') {
					index++;
					do {
						++index;
					} while (index < length && Character.isWhitespace(line.charAt(index)));
				}
			}
			return index;
		}
	}
	/**
	 * Text navigation action to navigate to the next sub-word.
	 * 
	 * @since 3.0
	 */
	protected abstract class NextSubWordAction extends TextNavigationAction {