[main] fix i3 protocol buf on error messages ("could not parse JSON")

Errors during startup currently cause bumblebee-status to mistakenly
output the first line of output (the "version" line) of the i3 protocol
twice, causing an error message that says "could not parse JSON")

see #940

bumblebee-status

@@ -100,6 +100,7 @@ def main():
     core.input.register(None, core.input.WHEEL_DOWN, "i3-msg workspace next_on_output")
 
     core.event.trigger("start")
+    started = True
 
     update_lock = threading.Lock()
     event_thread = threading.Thread(target=handle_events, args=(config, update_lock, ))
@@ -131,7 +132,6 @@ def main():
     if util.format.asbool(config.get("engine.collapsible", True)) == True:
         core.input.register(None, core.input.MIDDLE_MOUSE, output.toggle_minimize)
 
-    started = True
     signal.signal(10, sig_USR1_handler)
     while True:
         if update_lock.acquire(blocking=False) == True: