EffectLoader: Warn about trying to load an invalid effect

If the metadata of the effect is invalid, loadEffect will complain
rather than failing silently, making debugging issues a bit harder and
it's something that we are already checking for and shouldn't
realistically be happening.

src/effect/effectloader.cpp

@@ -324,9 +324,6 @@ QStringList PluginEffectLoader::listOfKnownEffects() const
 bool PluginEffectLoader::loadEffect(const QString &name)
 {
     const auto info = findEffect(name);
-    if (!info.isValid()) {
-        return false;
-    }
     return loadEffect(info, LoadEffectFlag::Load);
 }