[Keyman Developer] Bug when longpress popup > 30

**Describe the bug**
I was trying to add longpress popup keys, when several things didn't work as expected:

1. The display is only one row. This should be several rows (depending on windows size), because there's a lot of unused blank space below it
2. When adding several more keys after it reached the rightmost of the screen, the display go haywire, showing only white screen.
2b. The characters added to the right of that also invisible, even though I could add the characters from the Character Map window.
2c. Even after I scroll the popup bar to the right, or the window bar to the let, the empty space remains
2d. Changing tab (e.g. Details) and go back to Touch Layout tab also doesn't fix it.
2e. Only by closing the file and opening it again, the display is fixed, or close the out-of-bound boxes one by one.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to Keyman Developer
2. Click on a button, > "Add longpress popup"
3. Keep adding new keys to the right of that, and depending on your monitor, wait until it goes out of bound (mine did that after 25+)
3b Edit: After trying to reproduce it again, it seems adding empty boxes works as intended, but adding one empty box after the row is full, **then** adding a symbol from character map, create this bug.
4. See error

**Expected behavior**
1. Several rows of keys
2. It doesn't go infinitely to the right. Changing tab should refresh the display?
3. Adjustable height of window, maybe?

**Screenshots**
If applicable, add screenshots to help explain your problem.


---

(Delete the irrelevant sections)

**Keyman Developer:**
- OS: Windows 10
- Keyman Developer version: 12.0.66.0

---

**Keyboard**
- Any keyboard?