Fix HEDP cookoff null SoundDef

[N7Huntsman]

Additions

• Patch Bullet damageDef to have an explosion sound.

References

• Closes [Bug]: HEDP ammo detonation logs "SoundDef was null for DamageDef Bullet" #4499

Reasoning

• When these rounds cookoff, they use soundExplosion from the damageDef, which Bullet doesn't have since in vanilla the damage type isn't otherwise tied to explosions. Set it to use the same soundDef as the Bomb damage type.

Alternatives

• Could rework the cookoff sound to use cookOffSound as sent in xml rather than the explosion sound, as the code currently doesn't appear to support this.

Testing

Check tests you have performed:

• Compiles without warnings
• Game runs without errors
• (For compatibility patches) ...with and without patched mod loaded
• Playtested a colony (specify how long)

[github-actions]

You can download the rebuilt assembly for this PR here: https://combatextended.lp-programming.com/CombatExtended-23407085025.zip