qseecom:  Check for case where listener service is not found

When listerner service is not in the list of registered listeners,
the resulting ptr will a NULL. Check for this case of NULL ptr
to indicate missing listener service.

Change-Id: I0d2c7b01143c40711f71bf434493ac5301314cf2
Signed-off-by: Mona Hossain <mhossain@codeaurora.org>
Signed-off-by: Zhen Kong <zkong@codeaurora.org>
diff --git a/drivers/misc/qseecom.c b/drivers/misc/qseecom.c
index ac67c9d..af6c2e9 100644
--- a/drivers/misc/qseecom.c
+++ b/drivers/misc/qseecom.c
@@ -570,6 +570,11 @@
 		}
 		spin_unlock_irqrestore(&qseecom.registered_listener_list_lock,
 				flags);
+
+		if (ptr_svc == NULL) {
+			pr_err("Listener Svc %d does not exist\n", lstnr);
+			return -EINVAL;
+		}
 		if (ptr_svc->svc.listener_id != lstnr) {
 			pr_warning("Service requested for does on exist\n");
 			return -ERESTARTSYS;