Fix recent coverity scan warnings

Description of work

This PR fixes several coverity scan defects that have been logged since the renaming of some of the Indirect/Inelastic files. These defects have been around for a long time and have only been logged now because of the change to the name of these files triggering a coverity scan on these files.

To test:

Follow the testing instructions here https://developer.mantidproject.org/Testing/Inelastic/QENSFittingTests.html

This does not require release notes because this is not a user-facing change

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Functional Tests

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mantidproject / mantid