Initialize old_step_info_ptr to avoid stray memory reference.

Add step_id filtering as needed if a user requests info about a step_id
of zero (e.g. 123.0, it used to report all steps for the specified job_id).

src/scontrol/scontrol.c

@@ -705,17 +705,19 @@ static void
 _print_step (char *job_step_id_str)
 {
 	int error_code, i;
-	uint32_t job_id = 0, step_id = 0;
+	uint32_t job_id = 0, step_id = 0, step_id_set = 0;
 	char *next_str;
 	job_step_info_response_msg_t *job_step_info_ptr;
 	job_step_info_t * job_step_ptr;
 	static uint32_t last_job_id = 0, last_step_id = 0;
-	static job_step_info_response_msg_t *old_job_step_info_ptr;
+	static job_step_info_response_msg_t *old_job_step_info_ptr = NULL;
 
 	if (job_step_id_str) {
 		job_id = (uint32_t) strtol (job_step_id_str, &next_str, 10);
-		if (next_str[0] == '.')
+		if (next_str[0] == '.') {
 			step_id = (uint32_t) strtol (&next_str[1], NULL, 10);
+			step_id_set = 1;
+		}
 	}
 
 	if ((old_job_step_info_ptr) &&
@@ -761,6 +763,8 @@ _print_step (char *job_step_id_str)
 
 	job_step_ptr = job_step_info_ptr->job_steps ;
 	for (i = 0; i < job_step_info_ptr->job_step_count; i++) {
+		if (step_id_set && (step_id == 0) && (job_step_ptr[i].step_id != 0)) 
+			continue;
 		slurm_print_job_step_info (stdout, & job_step_ptr[i], one_liner ) ;
 	}