esql_model & esql_model_table: The way I implemented property_set and properties_load mandates:

I need to fall in error when old string is equal new string because it may come from properties_load,
in such case we'll only update the load status because the following pattern may be valid:

property_set(string1..)
property_set(string2..)
property_set(string3..)
properties_load() // relies on property_set for each property.