"Literal Value" leads to error

[ekrebs5]

Describe the bug
This check leads to a "symbols cannot be modified" error

To Reproduce
Steps to reproduce the behavior:

1. Open SwaLint
2. Execute "Literal Value" check (spelling)
3. Error instead of feedback

Expected behavior
The test is run and I get feedback.

Screenshots

Desktop (please complete the following information):

• OS: Linux
• Squeak image version Swa18
• SwaLint version Swa18

Additional context
Also happened to a SwaStudent

[ekrebs5]

Method selectors apparently as well?

[LinqLover]

This was apparently already fixed on branch develop before opening this issue, but should be ported back to RB.