Fix stack overflow error due to invalid condition

[MohamedAlmaki]

Description of work

This PR fixes a stack overflow error in ConfigService due to an invalid condition causing infinite recursion in the function makeAbsolute.

Fixes #38704

Further detail of work

In the splitPath function, the previous condition was only checking for the ";" delimiter. This causes makeAbsolute to call itself infinitely when the string contains only "," delimiters. I have corrected the function to include the "," delimiter, similar to the condition in make absolute, to ensure consistency.

To test:

1- Run this line in the Python script area:
ConfigService.setDataSearchDirs("/archive/NDXSANS2D/user/masks/,/archive/NDXSANS2D/user/Masks/")
2- It should work well without a crash
3- Check the data search dirs in Manage directories to ensure the two paths have been added correctly
4- Try different paths with combinations of "," and ";"

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[GuiMacielPereira]

Fix makes sense. I tested with one comma as suggested and then with several combinations of , and ;, and it worked fine with no issues.

[cailafinn]

Quick note on the code about using a constant instead of literals.

Additionally, It looks like this could benefit from a test or two - and it needs a release note as the bug was user-facing.

[cailafinn]

These two needing to be in sync has the potential to cause issues down the line. Can we make a constant called PATH_DELIMITERS or something that can be used in both places so this is less likely to happen again?