can't use command `move to workspace` in ipc

[jerrymaolong]

{'clientMessage': 'command "move to workspace 4"', 'success': False, 'messageType': 'client_response', 'data': None, 'er
ror': 'Object reference not set to an instance of an object.'}

i try to use ipc to Customize something，some command like workspaces focus workspace work fine. but the command move to workspace doesn't work.