output_chrt_NWM exits early on proc 0 if no channel points found

[danrosen25]

I stumbled upon this issue because there was a bug in my hydro.namelist configuration that caused the output_chrt_NWM to think there aren't channel points.

https://github.com/NCAR/wrf_hydro_nwm_public/blob/master/trunk/NDHMS/Routing/module_NWM_io.F#L651

Expected Behavior

In the rare case that there aren't channel points either all processes need to return early or all processes need to continue through the end of the subroutine. There are several mpp_land_sync calls in this subroutine and the last sync will wait indefinitely because process 0 has already exited.
https://github.com/NCAR/wrf_hydro_nwm_public/blob/master/trunk/NDHMS/Routing/module_NWM_io.F#L1017

Current Behavior

mpp_land_sync waits indefinitely

Possible Solution

Throwing an error if channel points are zero, skipping over the rest of the output data on proc 0 instead of returning, returning fro all processors.

Steps to Reproduce (for bugs)

1. I accidentally set the AGGFACTRT to 1 and therefore the domain only looked for channel points in 10% of the Fulldom file, which was probably ocean. And the channel output flag is on.

Your Environment

• Version of the code used: Latest
• Operating System and version: Jet, CentOS Linux 7
• Compiler and version: Intel 18.0.5.274
• Other relevant information: