[BUG] Color-Scale in GUI wrong after re-optimization with different number of fractions

[wahln]

Describe the bug
After re-optimization with a different number of fractions, the color bar sticks with the previous dose units, while the dose itself is updated (as well as the viewer options and the remainder of the GUI). After one more change (i.e., slice) the numbers are correct.

To Reproduce
Steps to reproduce the behavior:

1. Create a photon plan with 30 fractions
2. Re-Optimize with e.g. 5 fractions
3. Check wrong colorbar scale and observe everything else is updated
4. Change the slice -> correct scale

Expected behavior
After re-optimization you should directly have the correct axis ticks for the colorbar.