Usually, this enum should only ever be compared with `==`.
Confusingly, however, to check if a strip is an effect, one must
'bitwise-and' it instead. This can backfire if e.g. one tries to do
(strip->type & STRIP_TYPE_IMAGE) which doesn't work.
Make sure we only ever 'and' against the type enum when checking if
it is an effect. There was only this one case that didn't adhere.
f16cc57409