Jira REST API Time Tracking Null

My below code is getting me a null pointer exception when I try to get time tracking for my issues , even if the issue have time tracking , I'm using this api:

        <groupId>com.atlassian.jira</groupId>

        <artifactId>jira-rest-java-client-api</artifactId>

        <version>2.0.0-m19</version>

    </dependency>

    <dependency>

        <groupId>com.atlassian.jira</groupId>

        <artifactId>jira-rest-java-client-core</artifactId>

        <version>2.0.0-m19</version>

    </dependency>

//

for (JiraFixVersion jiraFixVersion : listJiraFixVersionsProject) {
        Iterator<Issue> issues = JiraClientManager.getInstance().getSearchResultSet("project='" + jiraProject.getProjectName()
                + "' AND fixVersion =" + "'" + jiraFixVersion.getName() + "'").iterator();
        Integer sumEstimatedTimeHours = 0;
        while (issues.hasNext()) {
            Issue issue = issues.next();
            Integer estimatedTime =0;
            try {
//Here is NullPointerException
                TimeTracking timeTracking = issue.getTimeTracking();

                estimatedTime = timeTracking.getOriginalEstimateMinutes();
                System.out.println("ok "+issue.getKey());
            }catch(NullPointerException e){
                System.out.println("Time Tracking null "+ issue.getKey());
            }
            sumEstimatedTimeHours += estimatedTime;
        }
        returnMap.put(jiraFixVersion, sumEstimatedTimeHours);
    }

I solved this through getting my field with :

for (JiraFixVersion jiraFixVersion : listJiraFixVersionsProject) {

        Iterator<Issue> issues = JiraClientManager.getInstance().getSearchResultSet("project='" + jiraProject.getProjectName() + "' AND fixVersion =" + "'" + jiraFixVersion.getName() + "'" + " AND cf[10002] !=null").iterator();
        Double sumStoryPoints = 0.0;
        while (issues.hasNext()) {
            Issue issue = issues.next();
            String storyPoints = issue.getField("customfield_10002").getValue().toString();
            Double storyPointIssue = Double.parseDouble(storyPoints);
            sumStoryPoints += storyPointIssue;
        }
        returnMap.put(jiraFixVersion, sumStoryPoints);
    }

'customfield_1002' is the field that I wanted , but if you really want that object TimeTracking you have to make another server request wich will last some precious time , I will not recommend that , but I will show the code :

while (issues.hasNext()) {

            Issue issue = issues.next();
            try {
                Issue claim = JiraClientManager.getInstance().getRestClient().getIssueClient().getIssue(issue.getKey()).claim();
                TimeTracking timeTracking = claim.getTimeTracking();
                Integer estimatedTimeSeconds =(Integer) issue.getField("timeoriginalestimate").getValue();
                Double estimatedTimeHours = (estimatedTimeSeconds.doubleValue())/3600;
                System.out.println(estimatedTimeHours+" "+issue.getKey());
                sumEstimatedTimeHours += estimatedTimeHours;
            }catch(NullPointerException e){
                System.out.println("Time Tracking null "+ issue.getKey());
            }
        }