Issue Summary

Pie chart where the statistic type is based on an Assests Object field returns error 500 when no data is returned from the filter.

Steps to Reproduce

1. Create a new Assets Objects type field
2. Add it to issue types, make sure you do not add values
3. Add Pie Chart to dashboard
4. Set the Statistic type to the new field
5. Save the Pie chart.
6. Error returned: 
   Can not zip unordered stream `lhs`."

Expected Results

Returns with NONE 100% 

Actual Results

{
    "message": "Can not zip unordered stream `lhs`.",
    "status-code": 500,
    "stack-trace": ""
} 

Request URL:https://your-domain.atlassian.net/rest/gadget/1.0/statistics?filterId=<filter_ID>&statType=customfield_<field_ID> 
Request Method:GET
Status Code:500 Internal Server Error

Workaround

Steps:

As alternative add or use the Work item Statistics gadget

1. Add the Work item Statistics gadget
2. Apply same Filter and Statistic Type as in Pie Chart configurations