[REQ][Plugin handling] Tell user about failed initialization

[m^2]

Tried with a WDX plugin, possibly happens with all others.
When a plugin returns 0 in DllMain(DLL_PROCESS_ATTACH), TC doesn't receive a handle to it and cannot use it. In such case I would expect that it tells user that something's wrong with the plugin. Instead, TC acts as if the plugin was ok, but returned empty strings in all fields.

[ghisler(Author)]

I will check why this is done. If I remember correctly, I do this so TC can still run if a plugin has been deleted by the user, but not removed from the plugin list. In this case, loading of the plugin will also fail.