ccminer: argument fix for 10th device selection

ccminer.cpp

@@ -3596,7 +3596,7 @@ void parse_arg(int key, char *arg)
 			char* pch = strtok(arg,",");
 			opt_n_threads = 0;
 			while (pch != NULL && opt_n_threads < MAX_GPUS) {
-				if (pch[0] >= '0' && pch[0] <= '9' && pch[1] == '\0')
+				if (pch[0] >= '0' && pch[0] <= '9' && strlen(pch) <= 2)
 				{
 					if (atoi(pch) < ngpus)
 						device_map[opt_n_threads++] = atoi(pch);