st-hal: Add error handling check

Add error handling check for conf_levels.

Change-Id: Iaa4f786a4e0be71870b87a49787d3ec4c9750567
diff --git a/st_session.c b/st_session.c
index 1a9b630..10aef77 100644
--- a/st_session.c
+++ b/st_session.c
@@ -2653,6 +2653,11 @@
              * during only one remaining client model as there won't be a
              * merged model yet.
              */
+            if (!conf_levels) {
+                ALOGE("%s: ERROR. conf levels alloc failed", __func__);
+                status = -ENOMEM;
+                return status;
+            }
             memcpy(stc_ses->sm_info.cf_levels, conf_levels,
                    stc_ses->sm_info.cf_levels_size);