Fix debug argument concatenation

The buffer was shorter than the arguments given to it which caused a heap
buffer overflow.

server/core/gateway.cc

@@ -3322,7 +3322,7 @@ static bool handle_debug_args(char* args)
         size_t total_len = 1;
         for (int i = 0; debug_arguments[i].action != NULL; i++)
         {
-            total_len += strlen(debug_arguments[i].name) + 1;
+            total_len += strlen(debug_arguments[i].name) + 2;
         }
         char arglist[total_len];
         arglist[0] = '\0';