Graph Editor ZoomToFit fighting user

When using the middle mouse button for panning in a graph editor, the zoom/pan transition effect will not cancel before completion due to manual input, leading to UI/User competition in an undesirable UI experience.

It seems this is due to SNodePanel::OnMouseButtonDown missing a call to CancelZoomToFit within the middle mouse button block.

1. Open up a blueprint or animation blueprint editor.
2. Double click a function, or animation state such that the zooming/panning transition effect occurs.
3. Drag with the right mouse button before the effect completes.

Notice that the transition stops

Set Editor Preferences -> Graph Editors -> General Style -> Panning Mouse Button to 'Middle' or 'Right or Middle'.

Repeat steps 1-3 this time dragging with the middle mouse button.

Notice that the transition attempts to continue while fighting the user's manual drag.

Expected that the transition stops regardless of the set/used Mouse Button.