quartz: Check for NULL condition in FilterGraph2_Disconnect.

dlls/quartz/filtergraph.c

@@ -744,6 +744,9 @@ static HRESULT WINAPI FilterGraph2_Disconnect(IFilterGraph2 *iface, IPin *ppin)
 
     TRACE("(%p/%p)->(%p)\n", This, iface, ppin);
 
+    if (!ppin)
+       return E_POINTER;
+
     return IPin_Disconnect(ppin);
 }
 

dlls/quartz/tests/filtergraph.c

@@ -1593,6 +1593,9 @@ static void test_render_filter_priority(void)
     hr = IFilterGraph2_Render(pgraph2, ((TestFilterImpl*)ptestfilter)->ppPins[0]);
     ok(hr == S_OK, "IFilterGraph2_Render failed with %08x\n", hr);
 
+    hr = IFilterGraph2_Disconnect(pgraph2, NULL);
+    ok(hr == E_POINTER, "IFilterGraph2_Disconnect failed. Expected E_POINTER, received %08x\n", hr);
+
     get_connected_filter_name((TestFilterImpl*)ptestfilter, ConnectedFilterName2);
     ok(lstrcmp(ConnectedFilterName1, ConnectedFilterName2),
         "expected connected filters to be different but got %s both times\n", ConnectedFilterName1);