[Maintenance] [th01] Shootout lasers: Add a safe subscript wrapper

Part of P0193, funded by Ember2528.

th01/main/boss/b20j.cpp

@@ -1355,10 +1355,7 @@ void pattern_lasers_and_3_spread(void)
 		}
 		target_y = PLAYFIELD_BOTTOM;
 
-		// Quite a roundabout way of preventing a buffer overflow, but fine.
-		shootout_lasers[
-			(boss_phase_frame / INTERVAL) % SHOOTOUT_LASER_COUNT
-		].spawn(
+		shootout_laser_safe(boss_phase_frame / INTERVAL).spawn(
 			SWORD_CENTER_X, SWORD_CENTER_Y,
 			target_left, target_y,
 			(to_sp(8.5f) / 2), V_WHITE, 30, 5

th01/main/boss/b20m.cpp

@@ -1846,9 +1846,7 @@ void near pattern_radial_stacks_and_lasers(void)
 			target_y = polar_y(CENTER_Y, 600, angle);
 			mdrv2_se_play(7);
 			if((boss_phase_frame % 15) == 0) {
-				shootout_lasers[
-					((boss_phase_frame - 215) / 15) % SHOOTOUT_LASER_COUNT
-				].spawn(
+				shootout_laser_safe((boss_phase_frame - 215) / 15).spawn(
 					CENTER_X, CENTER_Y, target_x, target_y,
 					pattern_state.speed_multiplied_by_8, V_WHITE, 20, 4
 				);

th01/main/bullet/laser_s.hpp

@@ -126,6 +126,10 @@ extern CShootoutLaser shootout_lasers[SHOOTOUT_LASER_COUNT];
 	} \
 }
 
+// Quite a roundabout way of preventing buffer overflows, but fine.
+#define shootout_laser_safe(i) \
+	shootout_lasers[(i) % SHOOTOUT_LASER_COUNT]
+
 #define shootout_lasers_unput_and_reset_broken(i) { \
 	for(i = 0; i < SHOOTOUT_LASER_COUNT; i++) { \
 		shootout_lasers[i].unput_and_reset(); \