[CRASH] KLineEdit Crashes on an undo

[Richard Newton]

Hi,

A fix in KLineEdit::clear() which went in on 23 March (revision 1.143 
according to the WebCVS) can cause and KLineEdit to crash on an undo command.

The problem in KLineEdit (and until recently QLineEdit which did exactly what 
was done here) is that it screws up the undo function.  If you put some text 
in a lineedit and then do a clear followed by an undo, the behaviour is 
incorrect.  Worse is if the line of text is only one character, the after a 
clear followed by and undo, the program will segfault.

The fix in qt was to make the behaviour of clear equivalent to doing a select 
all followed by a delete.  This apparently causes some unwanted side effects, 
so another way needs to be found.

Thanks,

Ric.