When using a fractional point size as default value, enlarging it and shrinking it (ctrl++, ctrl+-) will not return to the original value.

Reproducible: Always

Steps to Reproduce:
1. Select a font (eg: 10)
2. Set a fractional point size that visually differs from the lower and upper integers (eg: 10,5)
3. return to the editor and write something
4. enlarge the font (ctrl++)
5. shrink the font (ctrl+-)


Actual Results:  
Notice that the font is not rendered in the original size (eg 10,5)

Expected Results:  
The font to be rendered in the original size (eg 10,5)