qcacld-3.0: Check for null wlan kobject and return if true

Fix for null object dereference. Check for null wlan
kobject and return if true.

Change-Id: I90477335c81d44b9cc2762dd4060d9447a0bdb66
CRs-Fixed: 2717466

core/hdd/src/wlan_hdd_sysfs_mem_stats.c

@@ -82,8 +82,10 @@ int hdd_sysfs_mem_stats_create(struct kobject *wlan_kobject)
 
 void hdd_sysfs_mem_stats_destroy(struct kobject *wlan_kobject)
 {
-	if (!wlan_kobject)
+	if (!wlan_kobject) {
 		hdd_err("Could not get wlan kobject!");
+		return;
+	}
 	sysfs_remove_file(wlan_kobject, &mem_stats_attribute.attr);
 }