Test blank account field verifiability (#20458)

* Test blank account field verifiability

This change tests the need for #20428, which ensures that we guard against a situation in which `at_xpath` returns `nil`.

* Test verifiability of blank fields for remote account profiles

This adds a counterpart test for remote account profiles' fields' verifiability when those fields are blank. I previously added the same test for local accounts.

spec/models/account/field_spec.rb

@@ -89,6 +89,14 @@ RSpec.describe Account::Field, type: :model do
           expect(subject.verifiable?).to be false
         end
       end
+      
+      context 'for text which is blank' do
+        let(:value) { '' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
     end
 
     context 'for remote accounts' do
@@ -133,6 +141,14 @@ RSpec.describe Account::Field, type: :model do
           expect(subject.verifiable?).to be false
         end
       end
+      
+      context 'for text which is blank' do
+        let(:value) { '' }
+
+        it 'returns false' do
+          expect(subject.verifiable?).to be false
+        end
+      end
     end
   end
 end