Fix inventory items unresponsive after tab interaction until LMB click on formspec

[sfence]

• Goal of the PR
  Fix Inventory items unresponsive after tab interaction until LMB click on formspec #14250
• How does the PR work?
  Set m_held_mouse_button to BET_OTHER when the mouse UP event happens over tab control.
• Does it resolve any reported issue?
  Inventory items unresponsive after tab interaction until LMB click on formspec #14250

To do

Ready for Review.

How to test

See #14250

[appgurueu]

Tested, works. Logic checks out. Thanks.

[grorp]

I don't like this because the inventory handling leaks into an entirely unrelated part of the code. (m_held_mouse_button was introduced by #13146 and is only used by the inventory code.)

But hey, it works... Not approving or disapproving, I'm just annoyed by the amount of smell in the formspec code.

[sfence]

I don't like this because the inventory handling leaks into an entirely unrelated part of the code. (m_held_mouse_button was introduced by #13146 and is only used by the inventory code.)

But hey, it works... Not approving or disapproving, I'm just annoyed by the amount of smell in the formspec code.

I can move the m_held_mouse_button resetting code to some method like OnEvent_reset` or similar if it will be more clear.

[appgurueu]

It does seem like #13146 introduced some code smells, but I don't think it should be the job of this PR to refactor that. I don't think that introducing another function for this single assignment (?) will help clarity.