Allow icom read_frame to return when bus collision occurs

https://github.com/Hamlib/Hamlib/issues/1280

rigs/icom/frame.c

@@ -540,7 +540,8 @@ static int read_icom_frame_generic(hamlib_port_t *p,
             && (rxbuffer[read - 1] != COL));
 
     // Check that we have a valid frame preamble (which might be just a single preable character)
-    if (rxbuffer[0] != PR)
+    // Or an error code
+    if (rxbuffer[0] != PR && rxbuffer[0] != COL)
     {
         return -RIG_EPROTO;
     }

rigs/icom/icom.h

@@ -35,7 +35,7 @@
 #include <sys/time.h>
 #endif
 
-#define BACKEND_VER "20230425"
+#define BACKEND_VER "20230426"
 
 #define ICOM_IS_ID31 rig_is_model(rig, RIG_MODEL_ID31)
 #define ICOM_IS_ID51 rig_is_model(rig, RIG_MODEL_ID51)