Revert "Mark methods that should not be overwritten final"

This reverts commit c4e752aeba237cec66d4c106350f644633d1ce48.
Fix bad class reporting when null is passed to validate

Passing a non-object to get_class() is forbidden, and passing null to it returns the object the method is called in :(
Revert "Merge branch 'feature/fix-entityrepository-classname-reporting' into develop"

This reverts commit 657730df505846822ddd9b26d446ee235195d213, reversing
changes made to 667c3804ca80feb6641e9a1d3f26d00c2d6e1246.
Merge branch 'feature/fix-entityrepository-error-reporting' into develop