Fix priests and shopkeepers moving on other monsters

doc/fixes36.3

@@ -180,6 +180,7 @@ avoid 'object lost' panic when polymorph causes loss of levitation boots or
 fix exploding land mine moving ball or chain and causing a sanity error
 fix firing attached iron ball when swallowed causing a sanity error
 fix vault guard impossible when he could not relocate in certain situation
+fix temple priests or shopkeepers moving over other monsters
 
 
 Fixes to Post-3.6.2 Problems that Were Exposed Via git Repository

src/priest.c

@@ -118,6 +118,8 @@ pick_move:
     }
 
     if (nix != omx || niy != omy) {
+        if (MON_AT(nix, niy))
+            return 0;
         remove_monster(omx, omy);
         place_monster(mtmp, nix, niy);
         newsym(nix, niy);