Trying to delete malformed default input value or an input crashes Issie

[iridiium]

Describe the bug
When unsupported characters are entered into the default input value for an input, or the input is left blank, and then backspace is pressed, Issie will crash. for some projects, Issie will immediately crash every time the project is opened again, rendering it unusable.

To Reproduce
Steps to reproduce the behavior:

1. Make a new project
2. Add a new input with all values default
3. At the end of the default 0, add a 2.
4. Press backspace.
5. Issie goes to a white screen. The window can be closed but is responsive to all other commands.

Expected behavior
Issie does not crash

Desktop (please complete the following information):

• OS: Windows 11
• Version v5.12.1

[iridiium]

For an unusuable project, the project can be used again if the input component is manually removed from the .dgm file.