[Rigo] avoid race with finally block and GC wrt file descriptors

It has been observed that subprocess.call() called by open_url()
might fail due to Error 9 (Bad File Descriptor) due to a race
between the garbage collector thread (run in the MainThread) and
our own subprocess.call() thread. For this reason, make sure to
call open_url() outside the try/finally block. This seems to be
enough.

rigo/rigo/ui/gtk3/widgets/notifications.py

@@ -561,7 +561,6 @@ class LicensesNotificationBox(NotificationBox):
                     tmp_f.write("-" * 79 + "\n")
                     tmp_f.write(license_text)
                     tmp_f.flush()
-                open_url(tmp_path)
             else:
                 const_debug_write(
                     __name__,
@@ -576,6 +575,9 @@ class LicensesNotificationBox(NotificationBox):
                     pass
             # leaks, but xdg-open is async
 
+        if tmp_path is not None:
+            open_url(tmp_path)
+
     def _on_license_activate(self, widget, uri):
         """
         License link clicked.