Patch Set 7: I would prefer that you didn't submit this

In a new repo you get this in the error log and no dialog.

java.lang.NullPointerException
at org.eclipse.jgit.lib.ObjectIdSubclassMap.index(ObjectIdSubclassMap.java:172)
at org.eclipse.jgit.lib.ObjectIdSubclassMap.get(ObjectIdSubclassMap.java:89)
at org.eclipse.jgit.revwalk.RevWalk.parseAny(RevWalk.java:727)
at org.eclipse.jgit.revwalk.RevWalk.parseCommit(RevWalk.java:660)
at org.eclipse.egit.ui.internal.actions.TagAction.getRevCommits(TagAction.java:155)
at org.eclipse.egit.ui.internal.actions.TagAction.execute(TagAction.java:86)