If field "% Done" is hidden, issue lists showing that field crash Redmine

[gc-olivierho]

1. Hide the field "% Done" (field_done_ratio) with your plugin
2. In a project's Issues tab, display a saved query showing that field
   -> Error 500
   In the log :
   ActionView::Template::Error (undefined method round' for "":String): app/helpers/application_helper.rb:1121:incollect'
   app/helpers/application_helper.rb:1121:in progress_bar' app/helpers/queries_helper.rb:148:incolumn_value'

This is due to query_column_patch.rb which returns "" (empty string) whatever field is hidden.

It would be more appropriate to test the field value type and return something appropriate.
For example,
def value_with_hidden(object)
val = object.send name
if object.respond_to?(:hidden_attribute_names)
hidden_fields = object.hidden_attribute_names.map {|field| field.sub(/_id$/, '')}
if hidden_fields.include?(name.to_s)
case val
when Fixnum
0
when Array
[]
else
""
end

fixes this problem (although maybe some more cases should be defined, I haven't gone through all possibilities).