Summary:

It appears that if we try to do a "Bulk Operation" to sub-tasks when accessing its Parent ticket, NPE will be shown after selecting the sub-tasks and click next.

Steps to Reproduce:

1. Log in to JIRA.
2. Access a ticket.
3. Create two sub-tasks with the "More" button.
4. Make sure that there is no other string on the URL after the issue key like "<JIRA Base URL>/browse/KAN-1"
5. At the "Sub-Tasks" option, click the Triple Dot and select "Bulk Operation"
6. Select the two sub-tasks and proceed to click next.

Expected Result:

The option of what kind of operation to be done will be listed.

Actual Result:

This appears instead:

With log snippet:

2018-07-23 14:31:59,422 http-nio-8017-exec-17 ERROR      [c.a.j.web.servlet.InternalServerErrorServlet] {errorId=84e3922f-f45a-48c7-abc1-031ad6c45706, interpretedMsg=, cause=java.lang.NullPointerException, stacktrace=java.lang.NullPointerException
    	at com.atlassian.jira.web.action.issue.bulkedit.BulkEdit1.lambda$getQuery$0(BulkEdit1.java:229) [classes/:?]
    	at java.util.Optional.orElseGet(Optional.java:267) [?:1.8.0_60]
    	at com.atlassian.jira.web.action.issue.bulkedit.BulkEdit1.getQuery(BulkEdit1.java:229) [classes/:?]
    	at com.atlassian.jira.web.action.issue.bulkedit.BulkEdit1.doValidation(BulkEdit1.java:106) [classes/:?]
    	at webwork.action.ActionSupport.validate(ActionSupport.java:391) [webwork-1.4-atlassian-30.jar:?]

Workaround:

Accessing the ticket through a filter or by searching the parent ticket from the issue navigator first seems able to make the operation works.