[SR-Users] set empty custom global variable

In Kamailio config I use empty global string variable local.trace_troubleshooting_net = "" descr "trace all SIP messages from given network"

When I check variable value I get blank string kamcmd cfg.get local trace_troubleshooting_net

I can set new value [root@host]# kamcmd cfg.sets local trace_troubleshooting_net "2600::/48" [root@host]# kamcmd cfg.get local trace_troubleshooting_net 2600::/48

Now I want to set the empty custom global variable using a command kamcmd cfg.sets group trace_troubleshooting_net "" But get error error: 400 - error at parameter 2: expected string type but record doesn't match type

How to properly set empty values?