Do not fail when a searched issue has no fields
Do not fail when a searched issue has no fields

When we do a search filtering on returned fields, such as:

  client.search_issues(jql, fields='id')

The raw return is something like:

  {u'expand': u'operations,versionedRepresentations,editmeta,changelog,renderedFields',
   u'id': u'10005',
   u'key': u'TEST-6',
   u'self': u'http://jira:8080/rest/api/2/issue/10005'}

As the requested 'id' is not part of the 'fields', there is no 'fields'
dict returned by the REST API.

pycontribs/jira,dwmarshall/pycontribs-jira,pycontribs/jira,dwmarshall/pycontribs-jira