Zuweisung im if() beseitigt

Change-Id: I0836e033cc5c6fa2668c4bbc3e9755263e771e05
diff --git a/std/spellbook.c b/std/spellbook.c
index c0ee294..6f65709 100644
--- a/std/spellbook.c
+++ b/std/spellbook.c
@@ -209,9 +209,6 @@
 
 int
 CanTrySpell(object caster, mapping sinfo) {
-  mapping rmap;
-  string res;
-
   if (caster->QueryProp(P_GHOST)) {
     caster->ReceiveMsg(
       "Als Geist kannst Du nicht zaubern.",
@@ -219,7 +216,9 @@
       MA_SPELL);
     return 0;
   }
-  if ((rmap=sinfo[SI_SKILLRESTR_USE])
+  string res;
+  mapping rmap=sinfo[SI_SKILLRESTR_USE];
+  if (mappingp(rmap)
       && (res=check_restrictions(caster,rmap)))
   {
     caster->ReceiveMsg(res, MT_NOTIFICATION|MSG_BS_DONT_WRAP, MA_SPELL);