Error -2206 on Async exec unit if outgoing or ReadWrite channel size is 0

[fmussi]

Describe the bug
Async VI Loop returns error -2206 if you create an execution unit with 0 outgoing and / or readWrite channels

To Reproduce
Create an execution unit with only incoming channel refs and deploy the Custom device. You'll see the Read and Write to hardware steps not executing. If you enable error and stop async VI on error you'll notice error -2206

Additional context
potential fix by reading FIFO only if outgoing ch size is > 0