Cannot drag explorer back into its view container

[jrieken]

Testing #174718

• open search viewlet
• drag explorer (activity icon) into search pane
• all explorer views are now in the search pane
• 🐛 it is not possible to drag the file/folder view back into the explorer

Screen.Capture.21.02.23.12.13.43.mp4

[jrieken]

verified since the empty explorer is gone