Fix Detecting to cope with no active frames on cx (281984, r=jst).

git-svn-id: svn://10.0.0.236/trunk@169208 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/js/src/jsobj.c

@@ -2368,6 +2368,8 @@ Detecting(JSContext *cx, jsbytecode *pc)
     JSOp op;
     JSAtom *atom;
 
+    if (!cx->fp)
+        return JS_FALSE;
     script = cx->fp->script;
     for (endpc = script->code + script->length; pc < endpc; pc++) {
         /* General case: a branch or equality op follows the access. */