Merge branch 'fix/timeoutOnUnknownCommands' into devel

Conflicts:
	src/octoprint/util/comm.py

src/octoprint/util/comm.py

@@ -1704,9 +1704,14 @@ class MachineCom(object):
 					if gcode is not None:
 						use_up_clear = True
 
-					# if we need to use up a clear, do that now
 					if use_up_clear:
+						# if we need to use up a clear, do that now
 						self._clear_to_send.clear()
+					else:
+						# Otherwise we need to tickle the read queue - there might not be a reply
+						# to this command, so our _monitor loop will stay waiting until timeout. We
+						# definitely do not want that, so we tickle the queue manually here
+						self._continue_sending()
 
 				finally:
 					# no matter _how_ we exit this block, we signal that we