GitHub pull request #2965 of commit 761d78997769e9c47cff1d42c91721bf4e89807d, no merge conflicts.sha1origin/pr/2965/mergeghprbActualCommit761d78997769e9c47cff1d42c91721bf4e89807dghprbActualCommitAuthorghprbActualCommitAuthorEmailghprbAuthorRepoGitUrlhttps://github.com/djosephsen/bcc.gitghprbTriggerAuthorghprbTriggerAuthorEmailghprbTriggerAuthorLoginyonghong-songghprbTriggerAuthorLoginMention@yonghong-songghprbPullId2965ghprbTargetBranchmasterghprbSourceBranchtutorial-nitGIT_BRANCHtutorial-nitghprbPullAuthorEmailghprbPullAuthorLogindjosephsenghprbPullAuthorLoginMention@djosephsenghprbPullDescriptionGitHub pull request #2965 of commit 761d78997769e9c47cff1d42c91721bf4e89807d, no merge conflicts.ghprbPullTitleExplicitly use NULL macro in dref checkghprbPullLinkhttps://github.com/iovisor/bcc/pull/2965ghprbPullLongDescriptionAs a new-person going through the tutorial myself, I thought it might be a little clearer to use the NULL macro in checks like these. This could be accompanied by a _thing to learn_ in lesson four to the effect of: _The verifier requires that pointer values derived from a map lookup must be checked for a null value before they can be dereferenced and used_ ghprbCommentBody[buildbot, test this please]ghprbGhRepositoryiovisor/bccghprbCredentialsId6d3daf13-69b8-48b1-9c8f-ec5353264113false<a title="Explicitly use NULL macro in dref check" href="https://github.com/iovisor/bcc/pull/2965">PR #2965</a>: Explicitly use NULL macro i...#54613712787460664bcc-pr #546546false5464369SUCCESS1592013452398https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/546/git546https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/label=fc25/546/546https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/label=fc26/546/546https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/label=fc27/546/546https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/label=fc28/546/546https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/label=ubuntu1604/546/546https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/label=ubuntu1710/546/546https://buildbot.iovisor.org/jenkins/user/sumanthk/my-views/view/all/job/bcc-pr/label=ubuntu1804/546/