Bounds check all entity getters that can return 0

The entity getters I'm referring to are entityclass::getscm(),
entityclass::getlineat(), entityclass::getcrewman(), and
entityclass::getcustomcrewman().

Even though the player should always exist, and the player should always
be indice 0, I wouldn't want to make that assumption. I've been wrong
before.

Also, these functions returning 0 lull you into a false sense of
security. If you assume that commands using these functions are fine,
you'll forget about the fact that `i` in those commands could be
potentially anything, given an invalid argument. In fact, it's possible
to index createactivityzone(), flipgravity(), and customposition()
out-of-bounds by setting `i` to anything! Well, WAS possible. I fixed it
so now they can't.

Furthermore, in the game.scmmoveme block in gamelogic(), obj.getplayer()
wasn't even checked, even though it's been checked in all other places.
I only caught it just now because I wanted to bounds-check all usages of
obj.getscm(), too, and that game.scmmove block also used obj.getscm()
without bounds-checking it as well.

desktop_version/src/Map.cpp

@@ -2077,8 +2077,11 @@ void mapclass::loadlevel(int rx, int ry)
 				//A slight varation - she's upside down
 				obj.createentity(249, 62, 18, 16, 0, 18);
 				int j = obj.getcrewman(5);
-				obj.entities[j].rule = 7;
-				obj.entities[j].tile +=6;
+				if (INBOUNDS_VEC(j, obj.entities))
+				{
+					obj.entities[j].rule = 7;
+					obj.entities[j].tile +=6;
+				}
 				//What script do we use?
 				obj.createblock(5, 249-32, 0, 32+32+32, 240, 5);
 			}