Fix a bug that cannot process pending requests when the queue is empty but it still remains in pending state
Fix a bug that cannot process pending requests when the queue is empty but it still remains in pending state

cheton/cnc,cheton/cnc,cncjs/cncjs,cheton/piduino-grbl,cheton/piduino-grbl,cheton/piduino-grbl,cncjs/cncjs,cheton/cnc,cncjs/cncjs