Cellular: Fix build problem if cellular.debug-at is set as null

Author: Kimmo Vaisanen

features/cellular/framework/device/ATHandler.cpp

@@ -35,6 +35,10 @@ using namespace mbed_cellular_util;
 
 #include "CellularLog.h"
 
+#ifndef MBED_CONF_CELLULAR_DEBUG_AT
+#define MBED_CONF_CELLULAR_DEBUG_AT 0
+#endif
+
 // URCs should be handled fast, if you add debug traces within URC processing then you also need to increase this time
 #define PROCESS_URC_TIME 20
 

features/cellular/mbed_lib.json

@@ -14,7 +14,7 @@
             "value": 0
         },
         "debug-at": {
-            "help": "Enable AT debug prints. Note! This can have impact on UART performance and might need increasing of drivers.uart-serial-rxbuf-size",
+            "help": "Enable AT debug prints. Requires also mbed-trace to be enabled. Note! This can have impact on UART performance and might need increasing of drivers.uart-serial-rxbuf-size",
             "value": false
         },
         "radio-access-technology": {