Spray Can spawning rule cleanup

- You can spawn in Tutorial Challenge, but only if a single can has been picked up already
- Don't print a (DEVELOP-only, but still annoying) error when it doesn't spawn in Tutorial Challenge

src/p_mobj.c

@@ -13095,7 +13095,7 @@ static boolean P_SetupSpawnedMapThing(mapthing_t *mthing, mobj_t *mobj)
 	{
 		if (nummapspraycans == UINT8_MAX
 		|| modeattacking != ATTACKING_NONE
-		|| tutorialchallenge == TUTORIALSKIP_INPROGRESS)
+		|| (tutorialchallenge == TUTORIALSKIP_INPROGRESS && gamedata->gotspraycans == 0))
 		{
 			P_RemoveMobj(mobj);
 			return false;

src/p_setup.cpp

@@ -881,7 +881,8 @@ static void P_SpawnMapThings(boolean spawnemblems)
 
 	if (spawnemblems
 		&& gametype != GT_TUTORIAL
-		&& !modeattacking)
+		&& !modeattacking
+		&& !(tutorialchallenge == TUTORIALSKIP_INPROGRESS && gamedata->gotspraycans == 0))
 	{
 		const UINT8 recommendedcans =
 #ifdef DEVELOP