me again

anyone can make a sense on:
Qt Code:
  1. C:/Users/Tobias/Desktop/Schule/AINF/Diplomarbeit/New01/acting_class.h:21: error: field 'dia_job' has incomplete type
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qreator says so, but actually i didn't change anything, or just changed something at the ui, then changed is back and now it won't work anymore

i hope someone is able to help