Middle click for dragging canvas doesn't work.

[morgan55555]

Drag'n'drop canvas with middle mouse click doesn't work. "if (LiteGraph.middle_click_slot_add_default_node)" at line 803 in CanvasEvents.ts completely blocking drag'n'drop, 'cause it's condition is "else if". Fixed it locally by adding "skip_action = true;" to middle click node adding code and removed "else", but not sure, JS is not my favorite language. CanvasEvents.zip