An error I came across in the demo, after some updates, follows the information:
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FATAL ERROR in
action number 1
of Step Event0
for object obj_player:
REAL argument is unset
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called from - gml_Script_create_glass_ball (line 20)
called from - gml_Object_obj_player_Step_0 (line 964)
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The error happened when trying to use the glass ball made before the updates, in the base with no enemies nearby inside the house.