The template tests disable NOTICEs for the duration of template execution since
the current version of the template engine does not generate sufficiently clean
code. The error level is reset aftwards, however that part is skipped when
trigger_error is called which is converted into a regular exception by PHPUnit
and passed down until caught. Such exceptions are now caught to reset the error
level, and then the exception is rethrown.
This uncovered another issue in the template tests which only passed because
NOTICEs were unintentionally disabled at this point. assign_display is also
required to operate without NOTICEs. The respective code has been added around
its callee as well. However no handling of exceptions takes place there. If
another test checking for errors in that function is ever added similar catch
logic will have to be added there.
PHPBB3-9701
