fix(radio): '---' option is missing when selecting some source values. #11919

Job	Run time
Run tests (x9dp2019)	2m 56s
Run tests (tx16s)	5m 3s
Run tests (nv14)	5m 9s
Run tests (el18)	4m 56s
Run tests (pl18)	5m 9s
Run tests (pl18ev)	5m 7s
Run tests (t12)	2m 39s
Run tests (t12max)	2m 41s
Run tests (t15)	5m 4s
Run tests (t16)	5m 9s
Run tests (t18)	5m 0s
Run tests (t8)	2m 35s
Run tests (tlite)	2m 51s
Run tests (t20)	2m 40s
Run tests (t14)	2m 42s
Run tests (t20v2)	2m 47s
Run tests (tx12)	2m 41s
Run tests (x10)	5m 2s
Run tests (x12s)	5m 5s
Run tests (x7)	2m 52s
Run tests (x9d)	2m 31s
Run tests (x9dp)	2m 36s
Run tests (x9e)	2m 39s
Run tests (x9lite)	2m 35s
Run tests (x9lites)	2m 38s
Run tests (xlite)	2m 42s
Run tests (xlites)	2m 43s
Run tests (mt12)	2m 42s
Run tests (gx12)	2m 44s
Run tests (nb4p)	4m 57s
Run builds (nv14;el18)	5m 19s
Run builds (pl18;pl18ev)	5m 35s
Run builds (t12;t12max)	2m 31s
Run builds (t15;t16;t18)	7m 56s
Run builds (t8;zorro;pocket;mt12;commando8)	5m 22s
Run builds (tlite;tpro;tprov2;tpros;bumblebee;lr3pro)	6m 15s
Run builds (t20;t20v2;t14)	3m 23s
Run builds (tx12;tx12mk2;boxer;gx12)	4m 37s
Run builds (tx16s)	3m 7s
Run builds (f16)	3m 15s
Run builds (v16)	3m 9s
Run builds (x10;x10express)	5m 28s
Run builds (x12s)	3m 9s
Run builds (x7;x7access)	2m 29s
Run builds (x9d;x9dp;x9dp2019)	3m 22s
Run builds (x9e;x9e-hall)	2m 42s
Run builds (x9lite;x9lites)	2m 35s
Run builds (xlite;xlites)	2m 30s
Run builds (mt12;gx12)	2m 53s
Run builds (nb4p)	3m 18s
Package firmwares	7s
	3h 5m 57s

Provide feedback