riched20: Return E_INVALIDARG for empty ppSel in ITextDocument::GetSelection.

dlls/riched20/richole.c

@@ -515,6 +515,9 @@ ITextDocument_fnGetSelection(ITextDocument* me, ITextSelection** ppSel)
 {
     IRichEditOleImpl *This = impl_from_ITextDocument(me);
     TRACE("(%p)\n", me);
+
+    if(!ppSel)
+      return E_INVALIDARG;
     *ppSel = &This->txtSel->ITextSelection_iface;
     ITextSelection_AddRef(*ppSel);
     return S_OK;

dlls/riched20/tests/richole.c

@@ -117,6 +117,9 @@ static void test_Interfaces(void)
   ok(hres == S_OK, "IRichEditOle_QueryInterface\n");
   ok(txtDoc != NULL, "IRichEditOle_QueryInterface\n");
 
+  hres = ITextDocument_GetSelection(txtDoc, NULL);
+  ok(hres == E_INVALIDARG, "ITextDocument_GetSelection: 0x%x\n", hres);
+
   ITextDocument_GetSelection(txtDoc, &txtSel);
 
   punk = NULL;