Fix known issues discovered with compiler warnings

Description

Fixes #58 (closed), #57 (closed), #20 (closed) and #19 (closed). Few different cases:

• The involved code paths were probably crashing -> throw instead
• There was a clear intent that the code failed to achieve -> fix the code

Related Issue

Closes #58 (closed), #57 (closed), #20 (closed) and #19 (closed).

How Has This Been Tested?

Code compiles.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.