Default widget width not defined/looks broken

[beabehnisch]

Describe the bug
Compared with the earlier version, the new datapoint graph has a different default width define, which makes the widget look broken on default/whenever added

**To Reproduce
**
Steps to reproduce the behavior:

1. Edit widgets
2. Select new (vs. old) datapoint graph widget
3. Add

Expected behavior
a good default size that doesn't look broken/always require a resizing to be usable
(maybe even a minimum size, if the widget doesn't work smaller anyway)

Screenshots