Send size event after repopulating MeterToolbar buttons.

If we don't do this, it does not regain its former size, if it is floating.

src/prefs/PrefsDialog.cpp

@@ -394,6 +394,8 @@ void PrefsDialog::OnOK(wxCommandEvent & WXUNUSED(event))
          return;
    }
 
+   // flush now so toolbars will know their position.
+   gPrefs->Flush();
    if (mCategories) {
       // Now apply the changes
       for (size_t i = 0; i < mCategories->GetPageCount(); i++) {