In the change node, leave the value blank
and it is easy enough to test...
[{"id":"663ce662753eca2f","type":"change","z":"ea4605c08dd40eb0","name":"Refresh Browser","rules":[{"t":"set","p":"payload","pt":"msg","to":"","tot":"str"},{"t":"delete","p":"socketid","pt":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":590,"y":240,"wires":[["61d5cc7260ed2658"]]},{"id":"61d5cc7260ed2658","type":"debug","z":"ea4605c08dd40eb0","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":810,"y":240,"wires":[]},{"id":"32c524c6e4f3d416","type":"inject","z":"ea4605c08dd40eb0","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"blah","payloadType":"str","x":370,"y":240,"wires":[["663ce662753eca2f"]]}]