[lazarus] TTreeview problem

[Michal Bukovjan]

It seems there is a memory corruption somewhere.

The problem can be reproduced quite easily, just do:

1) Start Lazarus
2) Go to Environment -> CodeTools defines editor
3) Resize the windows slowly - either horizontally or vertically. Watch 
the treeview in upper part of the form.
4) Once the treeview reaches 0 size in either axis, crash occurs - 
invalid floating operation.

I tried to trace the problem with gdb, and it says it crashes at 
gtkcallback.inc, line 1919 (case of vertical scroll) - but that line is 
relatively inoccent. Looking at variables at that point, the values 
there are seemingly random, which I tend to believe is corrupted memory.

This appers under Linux and GTK, fpc 1.0.7

Michal