fix save several file on by reseting the xstorable on close

Change-Id: I329d43e06b0c81cebda0464ebb0fff41714020a3
Reviewed-on: https://gerrit.libreoffice.org/6355Reviewed-by: Tor Lillqvist <tml@collabora.com>
Tested-by: Tor Lillqvist <tml@collabora.com>

ios/shared/ios_sharedlo/cxx/mlo_uno.mm

@@ -365,6 +365,7 @@ mlo_close(void){
         openedXSelectionSupplier.clear();
         openedXFrame.clear();
         openedXDispatchProvider.clear();
+        openedXStorable.clear();
         resetLastSearch();
         
         NSLog(@"XComponent disposed successfully");