Fix crash when encountering invalid account fields (mastodon#16598)

* Add test

* Fix crash when encountering invalid account fields

Author: ClearlyClaire

app/models/account.rb

@@ -302,7 +302,11 @@ def also_known_as
   end
 
   def fields
-    (self[:fields] || []).map { |f| Field.new(self, f) }
+    (self[:fields] || []).map do |f|
+      Field.new(self, f)
+    rescue
+      nil
+    end.compact
   end
 
   def fields_attributes=(attributes)

spec/services/activitypub/process_account_service_spec.rb

@@ -12,6 +12,7 @@
         attachment: [
           { type: 'PropertyValue', name: 'Pronouns', value: 'They/them' },
           { type: 'PropertyValue', name: 'Occupation', value: 'Unit test' },
+          { type: 'PropertyValue', name: 'non-string', value: ['foo', 'bar'] },
         ],
       }.with_indifferent_access
     end