Return null BSTR from wxIAccessible if string returned from wxAccessible method is empty

wxIAccessible should return a NULL BSTR to the accessibility framework if strings returned from wxIAccessible::get_accName() and get_accValue() are empty because this convention is already applied to the other methods returning string values, like get_accHelp(), get_accDescription().

docs/changes.txt

@@ -143,6 +143,8 @@ wxMSW:
   errors in wxAccessible methods.
 - Return DISP_E_MEMBERNOTFOUND error code from wxIAccessible if wxAccessible
   methods return wxAccStatus::wxACC_NOT_SUPPORTED.
+- Return null BSTR from wxIAccessible if string returned from wxAccesible
+  method is empty.
 
 wxOSX:
 

src/msw/ole/access.cpp

@@ -1232,9 +1232,17 @@ STDMETHODIMP wxIAccessible::get_accName ( VARIANT varID, BSTR* pszName)
             return ((IAccessible*) m_pAccessible->GetIAccessibleStd())->get_accName (varID, pszName);
     }
     else
+    {
+        if ( name.empty() )
+        {
+            *pszName = NULL;
+            return S_FALSE;
+        }
+        else
         {
             wxBasicString basicString(name);
             *pszName = basicString.Get();
+        }
         return S_OK;
     }
     return E_NOTIMPL;
@@ -1405,11 +1413,19 @@ STDMETHODIMP wxIAccessible::get_accValue ( VARIANT varID, BSTR* pszValue)
             return ((IAccessible*) m_pAccessible->GetIAccessibleStd())->get_accValue (varID, pszValue);
     }
     else
+    {
+        if ( strValue.empty() )
+        {
+            *pszValue = NULL;
+            return S_FALSE;
+        }
+        else
         {
             wxBasicString basicString(strValue);
             * pszValue = basicString.Get();
             return S_OK;
         }
+    }
     return E_NOTIMPL;
 }