game: fix acid damage white flash bug

game/shared/hl2/hl2_gamerules.cpp

@@ -206,7 +206,7 @@ bool CHalfLife2::Damage_IsTimeBased( int iDmgType )
 	// Damage types that are time-based.
 #ifdef HL2_EPISODIC
 	// This makes me think EP2 should have its own rules, but they are #ifdef all over in here.
-	return ( ( iDmgType & ( DMG_PARALYZE | DMG_NERVEGAS | DMG_POISON | DMG_RADIATION | DMG_DROWNRECOVER | DMG_SLOWBURN ) ) != 0 );
+	return ( ( iDmgType & ( DMG_PARALYZE | DMG_NERVEGAS | DMG_POISON | DMG_RADIATION | DMG_DROWNRECOVER | DMG_ACID | DMG_SLOWBURN ) ) != 0 );
 #else
 	return BaseClass::Damage_IsTimeBased( iDmgType );
 #endif