[#1712] Reset fileNum when returning to title screen and prevent saving when file = 0xFF (#1721)

soh/src/code/z_play.c

@@ -2006,7 +2006,7 @@ s32 func_800C0DB4(GlobalContext* globalCtx, Vec3f* pos) {
 }
 
 void Gameplay_PerformSave(GlobalContext* globalCtx) {
-    if (globalCtx != NULL) {
+    if (globalCtx != NULL && gSaveContext.fileNum != 0xFF) {
         Gameplay_SaveSceneFlags(globalCtx);
         gSaveContext.savedSceneNum = globalCtx->sceneNum;
         if (gSaveContext.temporaryWeapon) {

soh/src/overlays/gamestates/ovl_opening/z_opening.c

@@ -10,6 +10,7 @@ void Opening_SetupTitleScreen(OpeningContext* this) {
     gSaveContext.gameMode = 1;
     this->state.running = false;
     gSaveContext.linkAge = 0;
+    gSaveContext.fileNum = 0xFF;
     Sram_InitDebugSave();
     gSaveContext.cutsceneIndex = 0xFFF3;
     gSaveContext.sceneSetupIndex = 7;