The SinceMutantFilter does not mark the unit test as changed if for any reason the TestFilePath is empty

[MischaVreeburg]

Describe the bug When the SinceMutantFilter is active and there are tests that do not have a TestFilePath, then these are never marked as having been changed and needing a rescan.

Expected behavior All covering tests that don't have a TestFilePath are marked as needing a rescan because Stryker is unable to determine if the file is part of the changeset and it is better to err on the side of caution in this case.

Desktop (please complete the following information):

• OS: Windows
• Type of project framework
• Framework Version : Net Framework 48
• Stryker Version 3.10