Warning in console

Hi there,
I am getting this warning, which seems to cause some problems in the backend:

 SimpLy Gallery Block v.1.0.0 
react.js?ver=16.9.0:260 Warning: Each child in a list should have a unique "key" prop.

Check the top-level render call using <div>. See https://fb.me/react-warning-keys for more information.
    in div
    in EditorProvider (created by WithDispatch(EditorProvider))
    in WithDispatch(EditorProvider)
    in Unknown (created by WithSelect(WithDispatch(EditorProvider)))
    in WithSelect(WithDispatch(EditorProvider))
    in Unknown (created by Context.Consumer)
    in WithRegistryProvider(WithSelect(WithDispatch(EditorProvider))) (created by Editor)
    in div (created by DropZoneProvider)
    in DropZoneProvider (created by Editor)
    in SlotFillProvider (created by Editor)
    in StrictMode (created by Editor)
    in Editor (created by WithDispatch(Editor))
    in WithDispatch(Editor)
    in Unknown (created by WithSelect(WithDispatch(Editor)))
    in WithSelect(WithDispatch(Editor))