Resolves: fdo#36678 regenerate language-specific user dict list

Regenerate language-specific user dict list when language of underlying text
changes. Not just when the user overrides it from the top menu.

cui/source/dialogs/SpellDialog.cxx

@@ -367,6 +367,7 @@ void SpellDialog::UpdateBoxes_Impl()
     else
         SetTitle_Impl( nAltLanguage );
     SetSelectedLang_Impl( nAltLanguage );
+    InitUserDicts();
 
     // Alternativen eintragen
     const ::rtl::OUString *pNewWords = aNewWords.getConstArray();