farsmile90
A very quick - and dirty - way of fixing your project is to open the
'maincode.xml' in the Event Sheet folder in a text editor, and delete the section causing the problem, which are the following lines at 15290-15923:
<action id="-11" name="Add to" sid="2833" type="HL_daugau1">
<param id="0" name="Instance variable">0</param>
<param id="1" name="Value">player</param>
</action>
Save, and the project will then open. You can the re-add whatever value you was trying to add to the instance variable.