Transform tool doesn't scale proportionnaly when using the height field after applying

[jazzynico]

Follow-up to Bug #1365405 "Scaling-Tool edit field for height not acting proportional"

0.92.1 r15371, Win7/64

Directly after applying (proportional) scaling, a new entry in the Height-field will not update the width field.

For example:
1. Draw a circle, select it
2. Transform (Shift+Ctrl+M)
3. Check "Scale proportionally"
4. Enter Width 50%, press Enter, Height-field will be updated
5. Apply (circle will be correctly reduced)
6. Enter Height 200%, press Enter, Width-field will NOT be updated
The Width-field gets updated only if you enter another value different from 200%.