Fix bugs with saved addresses (#122)

There were two issues leftover from the address refactoring:

- The company address select dropdown was trying to prefill with the contact address
- If we called saved_address.uprn and there was no saved_address, we got an error

This commit fixes those.

app/forms/address_form.rb

@@ -27,12 +27,17 @@ def look_up_addresses
 
   # If an address has already been assigned to the transient registration, pre-select it
   def preselect_existing_address
-    return unless @transient_registration.addresses.present?
-    return unless saved_address.uprn.present?
+    return unless can_preselect_address?
     selected_address = temp_addresses.detect { |address| address["uprn"] == saved_address.uprn.to_s }
     self.temp_address = selected_address["uprn"] if selected_address.present?
   end
 
+  def can_preselect_address?
+    return false unless saved_address
+    return false unless saved_address.uprn.present?
+    true
+  end
+
   def add_or_replace_address(selected_address_uprn)
     return if selected_address_uprn.blank?
 

app/forms/company_address_form.rb

@@ -19,7 +19,7 @@ def temp_postcode
   end
 
   def saved_address
-    @transient_registration.contact_address
+    @transient_registration.registered_address
   end
 
   def address_type