fix: change uid field in QCCollaborator to Optional[int] (#606)

Author: nelsonvega

lean/models/api.py

@@ -55,7 +55,7 @@ class ProjectEncryptionKey(WrappedBaseModel):
     name: str
 
 class QCCollaborator(WrappedBaseModel):
-    uid: int
+    uid: Optional[int]
     liveControl: bool
     permission: str
     profileImage: str