Missing monster graphics should not use replacement graphics

[Ghabry]

Name of the game:

Unterwegs in Düsterburg

Describe the issue in detail and how to reproduce it:

Reported by Käsekumpel at https://community.easyrpg.org/t/placeholder-graphics-for-missing-monster-files-can-disrupt-intended-game-design/972

This is kinda like the CBA-problem in Grimm's Hollow: The CBA was simply ignored when missing.
The same applies for monster graphics (for whatever reason...).

Default behaviour for missing Monster graphics should be simply to display nothing instead of a placeholder image. This seems to be a rare occurence where the RPG_RT exe won’t crash when missing a file.
The placeholder graphics are an issue in the final battle in Unterwegs in Düsterburg. The way Grandy implemented this battle is by referring to several placeholder graphics which he than deleted from his resource folder instead of just creating a completely transparent file. (Left Hand, Right Hand, Main Part of the boss…) The visuals of the boss are part of the backdrop image.
In RPG_RT nothing is drawn when a monster graphic is missing.