macintosh/windfarm_pm121.c: Fix for possible null pointer dereference

There is otherwise a risk of a possible null pointer dereference.

Was largely found by using a static code analysis program called cppcheck.

Signed-off-by: Rickard Strandqvist <[e-mail]>
Signed-off-by: Benjamin Herrenschmidt <[e-mail]>

drivers/macintosh/windfarm_pm121.c

···
 	pid_param.interval	= PM121_SYS_INTERVAL;
 	pid_param.history_len	= PM121_SYS_HISTORY_SIZE;
 	pid_param.itarget	= param->itarget;
-	pid_param.min		= control->ops->get_min(control);
-	pid_param.max		= control->ops->get_max(control);
+	if(control)
+	{
+		pid_param.min		= control->ops->get_min(control);
+		pid_param.max		= control->ops->get_max(control);
+	} else {
+		/*
+		 * This is probably not the right!?
+		 * Perhaps goto fail  if control == NULL  above?
+		 */
+		pid_param.min		= 0;
+		pid_param.max		= 0;
+	}
 
 	wf_pid_init(&pm121_sys_state[loop_id]->pid, &pid_param);
 
···
 	   control the same control */
 	printk(KERN_WARNING "pm121: failed to set up %s loop "
 	       "setting \"%s\" to max speed.\n",
-	       loop_names[loop_id], control->name);
+	       loop_names[loop_id], control ? control->name : "uninitialized value");
 
 	if (control)
 		wf_control_set_max(control);