Touchscreen: More erratic behaviour with multiple touches

[ChrisNZL]

Reported in 0.3.7k, and confirmed. Multiple touches trigger buttons incorrectly.

Likely a bug with my internal fingerId tracking, not resetting the fingerId when a button is no longer held, resulting in the fingerId persisting and being checked later on.

Unity's fingerId is typically 0, and then incremented by 1 if needed, but ultimately tries to return to 0 again for new touches when possible. So, fingerIds get reused — not good if they are not reset properly.

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• [x] Rough steps to reproduce & fix:

1. Using one finger, tap to open the Weapon Selector, then let go.
2. Tap the screen to close the Weapon Selector.
3. Hold a movement arrow, then tap the Jump button — the Weapon Selector will appear.

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• [x] Other issue, involving Hold to Attack and Hold to Jump:

1. Hold a movement arrow to move.
2. Hold Attack or Jump.
3. Let go of the movement arrow – attack/jump stops working.

• [x] Likewise:
  1. Hold Attack or Jump.
  2. Hold a movement arrow.
  3. Let go of Attack or Jump – movement stops working.

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• [x] Fourth issue – happens when releasing a touch AND starting a new touch on the same frame (easiest to reproduce with low frame rate):
  1. Hold jump button.
  2. Release jump button, then hold a movement arrow – movement does not occur.

[ChrisNZL]

0.3.7n: Fixed now, for real.