AttributeError: 'NoneType' object

Hi Guys, I recently upgraded our self hosted redash from V7.0.0.b18042 to V8.0.0.b32245 and i am seeing AttributeError: ‘NoneType’ object has no attribute ‘to_dict’ when i try to search the dashboards. it happens randomly. but doesn’t happen at all with queries, Every other thing works perfectly. How can i resolve this issue?