CLDC-3850: Clear postcode_known when clearing postcode_full (#2910)

* CLDC-3850: Clear postcode_known when clearing postcode_full

* Use different variables for lettings and sales postcode known

app/models/log.rb

@@ -248,6 +248,11 @@ def field_formatted_as_currency(field_name)
   end
 
   def blank_compound_invalid_non_setup_fields!
+    if errors.attribute_names.include? :postcode_full
+      self.postcode_known = nil if lettings?
+      self.pcodenk = nil if sales?
+    end
+
     self.ppcodenk = nil if errors.attribute_names.include? :ppostcode_full
     self.previous_la_known = nil if errors.attribute_names.include? :prevloc
 
@@ -258,6 +263,8 @@ def blank_compound_invalid_non_setup_fields!
       self.address_line2 = nil
       self.town_or_city = nil
       self.postcode_full = nil
+      self.postcode_known = nil if lettings?
+      self.pcodenk = nil if sales?
       self.county = nil
       process_postcode_changes!
     end