webhooks/jira: Avoid UnboundLocalErrors for event handler functions.
webhooks/jira: Avoid UnboundLocalErrors for event handler functions.

If the event key is None, the handler content_func never gets
defined, which leads to an UnboundLocalError. This can be easily
avoided by having a dedicated function that handles the case for
when the event key is None.

rht/zulip,kou/zulip,shubhamdhama/zulip,synicalsyntax/zulip,showell/zulip,andersk/zulip,kou/zulip,showell/zulip,rht/zulip,eeshangarg/zulip,rishig/zulip,rht/zulip,timabbott/zulip,hackerkid/zulip,kou/zulip,shubhamdhama/zulip,eeshangarg/zulip,zulip/zulip,hackerkid/zulip,tommyip/zulip,hackerkid/zulip,timabbott/zulip,shubhamdhama/zulip,punchagan/zulip,zulip/zulip,tommyip/zulip,synicalsyntax/zulip,rht/zulip,brainwane/zulip,eeshangarg/zulip,synicalsyntax/zulip,rishig/zulip,showell/zulip,timabbott/zulip,shubhamdhama/zulip,andersk/zulip,zulip/zulip,kou/zulip,andersk/zulip,eeshangarg/zulip,zulip/zulip,showell/zulip,kou/zulip,punchagan/zulip,showell/zulip,punchagan/zulip,brainwane/zulip,brainwane/zulip,synicalsyntax/zulip,punchagan/zulip,tommyip/zulip,eeshangarg/zulip,timabbott/zulip,tommyip/zulip,eeshangarg/zulip,rishig/zulip,zulip/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,brainwane/zulip,tommyip/zulip,kou/zulip,rht/zulip,tommyip/zulip,synicalsyntax/zulip,brainwane/zulip,hackerkid/zulip,rishig/zulip,rishig/zulip,synicalsyntax/zulip,timabbott/zulip,rht/zulip,hackerkid/zulip,synicalsyntax/zulip,andersk/zulip,andersk/zulip,shubhamdhama/zulip,brainwane/zulip,brainwane/zulip,shubhamdhama/zulip,eeshangarg/zulip,rishig/zulip,andersk/zulip,hackerkid/zulip,zulip/zulip,punchagan/zulip,timabbott/zulip,rht/zulip,shubhamdhama/zulip,punchagan/zulip,timabbott/zulip,kou/zulip,tommyip/zulip,rishig/zulip,punchagan/zulip,showell/zulip,showell/zulip