Add missing check to avoid passing handled input event to collision object 3d.

[Daylily-Zeleen]

Fix get_tree().root.set_input_as_handled() can't blocking event passing to input_event of CollisionObject3D.

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Here is MRP:
MRP.zip

[timothyqiu]

I think you can only check for is_input_handled() once before the 3D physics picking logic instead. (After the #ifndef on line 885.)

[akien-mga]

Thanks!