Input state is not reset when losing focus

[JordanSchlick]

The input state is not reset when losing focus which causes problems because the state of things can change while it is not focused.

In my case, I give input to the game when clicking the mouse and return it to ImGui when the mouse is released. ImGui never receives the mouse release because the game has consumed it. This makes it so that an additional mouse click is needed to to release to mouse state in ImGui before any other actions can be taken.

I think the input state should be reset in FImGuiInputState whenever ImGui loses focus unless there is a better way.

[WiggleWizard]

I vaguely remember screwing around with input reseting stuff when moving over to the new ImGui 1.87 input system. I'll take another peek at it and see if I can't fix it.