Bug fix: #3767 StringIndexOutOfBoundsException on HybridFile#getParent

[seelchen]

Description

Fix StringIndexOutOfBoundsException by checking if the end index given to the substring() function is negative. This can happen if the currentName does not occur in thisPath which causes the lastIndexOf() function to return -1.

Issue tracker

Fixes #3767

Automatic tests

• Added test cases

Manual tests

• Done

Build tasks success

Successfully running following tasks on local:

• ./gradlew assembledebug
• ./gradlew spotlessCheck

[seelchen]

This PR "fixes" the bug in a way that the StringIndexOutOfBoundsException won't be thrown but instead null is returned.
However, this probably does not address the root cause of the bug, which is that in some edge case the last element of pathSegments cannot be found in thisPath. Since the elements in pathSegments are constructed using thisPath, all of them should be contained in thisPath.
My guess is that maybe the elements in pathSegments are decoded (see documentation of getPathSegments()) and thisPath is still encoded, but I was not successful in finding a URI which could confirm my guess (I tried e.g. spaces vs +, but + was not decoded in thisPath nor pathSegments).