DnD from outside preview doesn't work for week / day cells

Check that this is really a bug

• I confirm

Reproduction link

https://jquense.github.io/react-big-calendar/examples/index.html?path=/story/addons-drag-and-drop--example-3

Bug description

1. Open https://jquense.github.io/react-big-calendar/examples/index.html?path=/story/addons-drag-and-drop--example-3
2. Check "Display dragged item in cell while dragging over"
3. Toggle week view
4. Drag item

Expected Behavior

DnD preview should work for hour specific events

Actual Behavior

DnD preview works only for all day events

react-big-calendar version

0.39.4

React version

17.0.2

Platform/Target and Browser Versions

Ubuntu Chrome

Validations

• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.
• Make sure this is a react-big-calendar issue and not an implementation issue

Would you like to open a PR for this bug?

• I'm willing to open a PR