Save config options for GPUs only if there are GPU devices.

main.c

@@ -3099,6 +3099,7 @@ static void write_config(FILE *fcfg)
 		}
 	fputs("\n],\n\n", fcfg);
 
+	if (nDevs) {
 		/* Write GPU device values */
 		fputs("\"intensity\" : \"", fcfg);
 		for(i = 0; i < nDevs; i++)
@@ -3130,6 +3131,7 @@ static void write_config(FILE *fcfg)
 			fprintf(fcfg, "%s%d", i > 0 ? "," : "", gpus[i].adl.targettemp);
 #endif
 		fputs("\",\n", fcfg);
+	}
 	fprintf(fcfg, "\n\"algo\" : \"%s\"", algo_names[opt_algo]);
 	
 	/* Simple bool and int options */