Drag cursor (and delete cursor) disappears from block after starting drag

[kchadha]

Expected Behavior

Drag cursor should remain on block while dragging.
Delete cursor should appear on block when dragging over the toolbox.

Actual Behavior

Neither of the two happen. This regression was introduced by #2584.

Behavior before regression:

Current Behavior:

[epicfaace]

@kchadha Undoing the change in #2584 fixes this; what problem, exactly, was #2584 supposed to fix?

[kchadha]

@epicfaace, #2584 fixed an issue where you couldn't share blocks to a sprite twice.

To Repro (without the changes in #2584):

1. Open a new 3.0 project
2. Create another sprite
3. Drag out a block from the toolbox into Sprite 1
4. Drag that block from Sprite1 into Sprite2
5. Without scrolling the workspace at all, try to drag that same block again from Sprite1 to Sprite2 again
6. Observe that Sprite 2 highlights, but its sprite tile does not wiggle (indicating that blocks can be shared to it)
7. Switch to Sprite 2, observe that it only has one instance of that shared block

Here is a gif:

[epicfaace]

@kchadha , #4184 should fix both issues #2584 and this one.

[adroitwhiz]

This is happening again because #5078 was reverted