Prevent 'Failed to dispatch .uno:None' message

This was seen when checking grammar checker suggestion.
When I click on the top element of the context menu of
underlined text (e.g. Grammar error), I get

warn:lok:1663798:1663791:desktop/source/lib/init.cxx:283:
lok exception 'Failed to dispatch .uno:None'

This .uno:None was introduced by Tamas Zolnai especially for
LOK: 3616bb68f2
His intention was to add an empty command that does nothing.

Change-Id: I12a9a1e17dcf65cdd78266f44e6201ed3d5fa01f
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/175102
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
(cherry picked from commit bdb0dd485da24a95b61df6136362ab189803bc27)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/175845
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Jenkins

desktop/source/lib/init.cxx

@@ -5346,6 +5346,9 @@ static void doc_postUnoCommand(LibreOfficeKitDocument* pThis, const char* pComma
     if (!isCommandAllowed(aCommand))
         return;
 
+    if (gImpl && aCommand == ".uno:None")
+        return;
+
     LibLODocument_Impl* pDocument = static_cast<LibLODocument_Impl*>(pThis);
 
     std::vector<beans::PropertyValue> aPropertyValuesVector(jsonToPropertyValuesVector(pArguments));