Enforce stricter checks on sequence Facings.

[pchote]

This prevents modders from setting Facings values that can cause the game to crash with an unhelpful IndexOutOfRangeException.

Consider Facings: 5. 1024 / 5 = 204.8 WAngle units for each sprite. The frame selection code rounds this down to 204 per frame, which then leaves angles 204 * 5 = 1020 through 1023 without associated artwork, causing a crash when something asks for that.

An alternative solution would be to non-uniformly map the facings to the angle range (4 of the 5 frames have 205 units, 1 with 204, or 5 with 204 and 1 with 208), but this would add a lot of complexity and probably a measurable performance hit. The responsibility is on modders to not pick silly frame values, but this does rely on the game telling them when they do it wrong.

[pchote]

Testcase: https://resource.openra.net/maps/54794

[PunkPun]

changelog