Describe the bug
When changing the units in the preferences from imperial to metric, the ruler units in the rocket design view don't dynamically update. You only see a change in units when you close the design and re-open it.

To Reproduce
Steps to reproduce the behavior:

1. Open any rocket design
2. Go to the OpenRocket preferences, to the units tab
3. Change the rocket dimensions unit, e.g. from in to cm
4. Close the preferences dialog
5. The ruler unit did not change.

Expected behavior
The ruler unit should be cm, not inch.

Screenshots

Platform

• OS: macOS
• OpenRocket version unstable