PLEASE HELP ME I CANNOT OPEN ANIMATOR MASK !!!

PLEASE HELP ME I CANNOT OPEN ANIMATOR MASK WHATS MY PROBLEM, IM USE UNITY 5.6.5 VERSION AND IM CHANGE MY VERSİONS WITH MY PROJECT AND I DONT KNOW WHAT IS THAT every time says me that C:Buildslave… error.

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aybody can help me ???