Problem description: 
When trying to set a font for multiple cells that have previously had different fonts the drop-down font selection menu can not be scrolled normally but instead constantly repositions the view to the top of the menu.

Steps to reproduce:
1. Open a new spreadsheet
2. Enter some text in a cell
3. Enter some text in an adjacent cell and change it's font to something different then the original one
4. Select both cells and try to change the font by clicking on the font menu and scrolling down.

Current behavior:
 During scrolling either with the mouse wheel or the slider, the view constantly jumps back to the top of the drop down menu. This makes selecting a font that is at the end of the list extremely hard. 

Expected behavior:
Scrolling down a menu should not result in being automatically put beck to the top. When all the fonts in the selected cells are the same the scrolling behaves as expected.

Further information: 
The problem has been noticed in both versions 4.2.6.2 and 4.3.1.2 on an Arch Linux distribution, not sure about older versions. 
Operating System: Linux (Other)
Version: 4.2.6.2 release