Physics objects don't detect the mouse if inside a sub-viewport

[YeldhamDev]

Godot version:
ba854bb

Issue description:
Physics objects (like Area2D, for example) inside sub-viewports aren't detecting any mouse inputs.

This was supposedly fixed in 26d33d1, but it's still reproducible as of now.

EDIT: _unhandle_inputs are also not being detected at all.

[lukaskotik]

Was it really fixed? In 3.2.1 I still have to use

func _input(event):
    $viewport.unhandled_input(event)

and if the scaling or size of viewport is different than is the project setting, event position have to first transformed.