If an add-on url is wrong it was throwing a php error

[intoeetive]

Better to throw a 404 than show an error (which was confusing).

We were getting a 'Call to a member function checkCachedLicenseResponse() on null' in Controller/Addons/Addons.php line 745 when we had a malformed add-on url. Tossed the other 404s in as well since they just made sense to me, but probably not needed.

(cherry picked from commit 1b52fe5ec74a8f20dd8e30619d07ce2de4d8c9a6)

EE7 version of https://github.com/ExpressionEngine/ExpressionEngine/pull/2120