Index: mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp
===================================================================
RCS file: /cvsroot/mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp,v
retrieving revision 1.17
diff -pU4 -r1.17 mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp
--- mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp
+++ mozilla/modules/plugin/base/src/nsJSNPRuntime.cpp
@@ -978,9 +978,9 @@ nsJSObjWrapper::GetNewOrUsed(NPP npp, JS
 
 static NPObject *
 GetNPObject(JSContext *cx, JSObject *obj)
 {
-  while (JS_GET_CLASS(cx, obj) != &sNPObjectJSWrapperClass) {
+  while (obj && JS_GET_CLASS(cx, obj) != &sNPObjectJSWrapperClass) {
     obj = ::JS_GetPrototype(cx, obj);
   }
 
   if (!obj) {
@@ -1150,9 +1150,9 @@ NPObjWrapper_GetProperty(JSContext *cx, 
 JS_STATIC_DLL_CALLBACK(JSBool)
 CallNPMethod(JSContext *cx, JSObject *obj, uintN argc, jsval *argv,
              jsval *rval)
 {
-  while (JS_GET_CLASS(cx, obj) != &sNPObjectJSWrapperClass) {
+  while (obj && JS_GET_CLASS(cx, obj) != &sNPObjectJSWrapperClass) {
     obj = ::JS_GetPrototype(cx, obj);
   }
 
   if (!obj) {