shell32: Avoid crash on NULL pointer.

dlls/shell32/assoc.c

@@ -84,6 +84,9 @@ static HRESULT WINAPI IQueryAssociations_fnQueryInterface(
 
   TRACE("(%p,%s,%p)\n",This, debugstr_guid(riid), ppvObj);
 
+  if (ppvObj == NULL)
+      return E_POINTER;
+
   *ppvObj = NULL;
 
   if (IsEqualIID(riid, &IID_IUnknown) ||

dlls/shell32/tests/assoc.c

@@ -54,6 +54,9 @@ static void test_IQueryAssociations_QueryInterface(void)
         IUnknown_Release(unk);
     }
 
+    hr = IUnknown_QueryInterface(qa, &IID_IUnknown, NULL);
+    ok(hr == E_POINTER, "got 0x%x (expected E_POINTER)\n", hr);
+
     IQueryAssociations_Release(qa);
 }