[Core: Module] Fix errors in 500-reponse logic

[johnsaigle]

Brief summary of changes

Instrument List crashes on bugfix because the $user variable was not properly set. A TypeError is thrown by responseStatus500() as a result.

This isn't clear from the code changes but this should fix errors like:
Fatal error: Uncaught TypeError: Argument 2 passed to Module::responseStatus500() must be an instance of User, null given, called in /home/travis/build/aces/Loris/php/libraries/Module.class.inc on line 309 and defined in /home/travis/build/aces/Loris/php/libraries/Module.class.inc:334

[johnsaigle]

In fixing the above error, instrument_list stopped working because of the way it handles its routing.

A 500 error would appear on the front-end and this exception was in the error log:
LorisException: Page requires a timepoint to load in /var/www/loris/modules/instrument_list/php/instrument_list.class.inc:85

as the code throws a LorisException when TimePoint or Candidate are missing from the request. However, this Exception ended up being caught by Module after #4163 was merged.

This code was changed to throw a NotFound exception instead so that the module routing code does not get returned.

If any of that was hard to understand it's worth reviewing instrument_list/php/module.class.inc and the handle function in php/libraries/Module.class.inc

[johnsaigle]

These were being caught by https://github.com/aces/Loris/pull/4163/files#diff-b9919f169806c905a8606fd31442044fR304, preventing instrument_list from loading.

[driusan]

@kongtiaowang can you manually test this?

[xlecours]

I think the $user parameter of the responseStatus500 function could be retrieved from the request instead of being injected.
Also, responseStatus500 should use the AnonymousPageDecorationMiddleware or UserPageDecorationMiddleware according to the class of user.
Arguably, the resulting response should be HTTP/1.1 400 Bad Request if the request is missing parameters.

[driusan]

Merging despite @xlecours's comment since the instrument list page needs the bug fix, and the feedback could be done in another PR..