Silence an "unused result" warning for the benchmark code.

src/tests/bench/bench_ph.c

@@ -254,8 +254,11 @@ main(int argc, char *argv[])
 			strerror(errno));
 		exit(EXIT_FAILURE);
 	}
-	(void)fread(seed, sizeof(uint32_t), 4, urandom);
-	if (ferror(urandom)) {
+	if (fread(seed, sizeof(uint32_t), 4, urandom) != 4) {
+		fprintf(stderr, "Failed to read 128 bits from /dev/urandom\n");
+		exit(EXIT_FAILURE);
+	}
+	else if (ferror(urandom)) {
 		fprintf(stderr, "Error reading /dev/urandom: %s\n",
 			strerror(errno));
 		exit(EXIT_FAILURE);