Crash/Freeze: Remove ElementUsage

[lxatstariongroup]

Prerequisites

• [x] I have written a descriptive issue title
• [x] I have verified that I am running the latest version of the COMET-IME
• [x] I have searched open and closed issues to ensure it has not already been reported

Description

Sometimes while removing an ElementUsage in a Model freezes, CPU goes wild and sometimes COMET even crashed. Exact circumstances are not clear. ElementDefinition browser was in all cases filtered on Category membership. Not sure if ProductTree was also open in all cases, but at least in a lot of cases. Model was quite large, in the sense that the treeviews in PT and ED browsers were quite big.

Related to #1327

System Configuration

• COMET version:
  • [ ] COMET-IME: 9.6.0