Get error connect XTL5000

[lloovve]

when I test this program on XTL5000 . then get a error

21:52:37.230 VRB] Got 1 indicator update(s)
[21:52:37.230 VRB] Codes: 56
[21:52:37.230 VRB] States: 01
[21:52:37.230 WRN] Could not find matching indidactor for code 56
[21:52:37.232 ERR] Got exception in SB9600 thread
System.NullReferenceException: Object reference not set to an instance of an object.
   at daemon.SB9600.processSBEP(Byte[] msgBytes) in /home/runner/work/RadioConsole2/RadioConsole2/daemon/MotorolaSB9600.cs:line 1283
   at daemon.SB9600.serialLoop(Object _token) in /home/runner/work/RadioConsole2/RadioConsole2/daemon/MotorolaSB9600.cs:line 1573