Prevent creation of config popup while dragging a block from a sidebar. It causes config popup not being openable after dragging existing blocks on the landing page workspace.

Steps to reproduce:
1. Edit existing landing page or create a new one,
2. Open the Elements tab in browser console,
3. Drag a new block from the sidebar and drop it onto a workspace,
4. Start dragging a new block around.

Expected result:
The config popup is not rendered and after clicking on the Settings button the config popup is opened.

Actual result:
The config popup is rendered (hidden, but rendered), despite of preview block not being rendered. After moving the block to other places in a zone/zones sometimes it's not possible to open a block config popup.