DB/Creatures: added default value for visibility distance override values

sql/updates/world/custom/custom_2019_01_11_00_world.sql

@@ -0,0 +1,5 @@
+ALTER TABLE `creature_template_addon`   
+  CHANGE `visibilityDistanceType` `visibilityDistanceType` TINYINT(3) UNSIGNED DEFAULT 0 NULL;
+
+ALTER TABLE `creature_addon`   
+  CHANGE `visibilityDistanceType` `visibilityDistanceType` TINYINT(3) UNSIGNED DEFAULT 0 NULL;