Set null columns to the default value prior to setting not null

deployment/hasura/migrations/AerieScheduler/7_definition_consistency/up.sql

@@ -1,9 +1,17 @@
 alter table scheduling_goal
-  alter column description set default '',
+  alter column description set default '';
+update scheduling_goal
+  set description = default
+  where description is null;
+alter table scheduling_goal
   alter column description set not null;
 
 alter table scheduling_condition
-  alter column description set default '',
+  alter column description set default '';
+update scheduling_condition
+  set description = default
+  where description is null;
+alter table scheduling_condition
   alter column description set not null;
 
 call migrations.mark_migration_applied('7');