bug 311403: Enforce JS engine invarients. r=brendan

js/src/jsscript.c

@@ -312,17 +312,15 @@ script_exec(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
 
     /* Belt-and-braces: check that this script object has access to scopeobj. */
     principals = script->principals;
-    if (principals) {
-        rt = cx->runtime;
-        if (rt->findObjectPrincipals) {
-            scopePrincipals = rt->findObjectPrincipals(cx, scopeobj);
-            if (scopePrincipals &&
-                !principals->subsume(principals, scopePrincipals)) {
-                JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
-                                     JSMSG_BAD_INDIRECT_CALL,
-                                     "Script.prototype.exec");
-                return JS_FALSE;
-            }
+    rt = cx->runtime;
+    if (rt->findObjectPrincipals) {
+        scopePrincipals = rt->findObjectPrincipals(cx, scopeobj);
+        if (!principals || !scopePrincipals ||
+            !principals->subsume(principals, scopePrincipals)) {
+            JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
+                                 JSMSG_BAD_INDIRECT_CALL,
+                                 "Script.prototype.exec");
+            return JS_FALSE;
         }
     }