[Kst] [Bug 143803] Kst crashes when using invalid vector

[Barth Netterfield]

Why are we talking about string changes? this is a bug in the KstComboBox.... 
it is suppose to act as a non-editable combo, and so it should never give you 
an invalid field name.

If you do the reported action (enter an invalid X axis tag name) and then do 
something that removed focus from the combo (like hit tab) rather than 
hitting OK straight away, then the field reverts to whatever it was before 
you tried to change it.  This is acceptable behavior.  However, changing the 
field, then hitting apply doesn't remove focus, so this check never happens.

The proper change is make sure that selectedVector() can never return a 
non-existant vector.  This should be very easy to fix, and should be fixed 
for 1.4.0.

Of course this leaves a UI bug: there is no visual indication that at any 
given moment, the combo box is in an invalid state.  A visual queue which 
made clear whether what you have typed in is even possible would be good... 
(a mini icon?  font change?  colour change?)  This is a 1.5 or 2.0 fix.