[SHELL32] Fix a couple of tests

dll/win32/shell32/CShellItem.cpp

@@ -250,6 +250,8 @@ HRESULT WINAPI SHCreateShellItem(LPCITEMIDLIST pidlParent,
 
     TRACE("(%p,%p,%p,%p)\n", pidlParent, psfParent, pidl, ppsi);
 
+    *ppsi = NULL;
+
     if (!pidl)
         return E_INVALIDARG;
 
@@ -291,7 +293,6 @@ HRESULT WINAPI SHCreateShellItem(LPCITEMIDLIST pidlParent,
     hr = CShellItem::_CreatorClass::CreateInstance(NULL, IID_PPV_ARG(IShellItem, &newShellItem));
     if (FAILED(hr))
     {
-        *ppsi = NULL;
         ILFree(new_pidl);
         return hr;
     }

dll/win32/shell32/folders/CDesktopFolder.cpp

@@ -819,6 +819,9 @@ HRESULT WINAPI CDesktopFolder::Initialize(LPCITEMIDLIST pidl)
 {
     TRACE ("(%p)->(%p)\n", this, pidl);
 
+    if (!pidl)
+        return S_OK;
+
     return E_INVALIDARG;
 }