Fixed occasional io thread hang on shutdown

RNS/Reticulum.py

@@ -173,6 +173,7 @@ class Reticulum:
         # classes, saving necessary information to disk and carrying
         # out cleanup operations.
         if not Reticulum.__exit_handler_ran:
+            Reticulum.__exit_handler_ran = True
             if not Reticulum.__interface_detach_ran:
                 RNS.Transport.detach_interfaces()
             RNS.Transport.exit_handler()

RNS/__init__.py

@@ -373,7 +373,6 @@ def exit(code=0):
     global exit_called
     if not exit_called:
         exit_called = True
-        print("")
         Reticulum.exit_handler()
         os._exit(code)