Flamebreak 1.5.19: Input Crash & Music Loop Fix

This hotfix resolves a crash caused by unmapped input keys and fixes an audio issue where victory/level-complete music could get stuck looping a short segment on some systems, so the full track now plays as intended.

• Fixed a crash caused by polling an unmapped/unknown input key, preventing the "GLFW error (65539): Invalid key -1" exception seen in 1.5.18.

• Fixed an issue where victory/level-complete music could get stuck repeating the same short segment on some systems, so the full track now plays smoothly.