Fix model array (#3421)

packages/core/src/objvalue.ts

@@ -1,6 +1,7 @@
 import { PlatformError, Severity, Status } from '@hcengineering/platform'
 import { Doc } from './classes'
 import core from './component'
+import justClone from 'just-clone'
 
 /**
  * @public
@@ -59,7 +60,7 @@ export function setObjectValue (key: string, doc: Doc, newValue: any): void {
       value = lvalue
     }
   }
-  value[last] = newValue
+  value[last] = justClone(newValue)
   return value
 }