Merge pull request scp-fs2open#7341 from Goober5000/fix/mission_loop_music

fix mainhall music continuing to play during mission loop brief

Author: Goober5000

code/missionui/missionloopbrief.cpp

@@ -94,7 +94,7 @@ int Loop_brief_bitmap;
 
 generic_anim Loop_anim;
 
-int Loop_sound;
+int Loop_sound = -1;
 
 // ---------------------------------------------------------------------------------------------------------------------------------------
 // MISSION LOOP BRIEF FUNCTIONS
@@ -127,6 +127,9 @@ void loop_brief_init()
 	int idx;
 	ui_button_info *b;
 
+	// init sound handle
+	Loop_sound = -1;
+
 	// load the background bitmap
 	Loop_brief_bitmap = bm_load(Loop_brief_fname[gr_screen.res]);
 	Assert(Loop_brief_bitmap != -1);

freespace2/freespace.cpp

@@ -6293,6 +6293,10 @@ void mouse_force_pos(int x, int y);
 			break;		
 
 		case GS_STATE_LOOP_BRIEF:
+			if (old_state == GS_STATE_MAIN_MENU) {
+				main_hall_stop_music(true);
+				main_hall_stop_ambient();
+			}
 			loop_brief_init();
 			break;