Avoid null deref in command line arg processing. Reported by lfm.
diff --git a/cpu-miner.c b/cpu-miner.c
index a47d77a..ab7ea1a 100644
--- a/cpu-miner.c
+++ b/cpu-miner.c
@@ -328,7 +328,8 @@ static void parse_arg (int key, char *arg)
switch(key) {
case 'a':
for (i = 0; i < ARRAY_SIZE(algo_names); i++) {
- if (!strcmp(arg, algo_names[i])) {
+ if (algo_names[i] &&
+ !strcmp(arg, algo_names[i])) {
opt_algo = i;
break;
}