NMS-7083: Do not get OnmsSnmpInterface if ifindex is null.
NMS-7083: Fix NullPointer when lastPollTime is null.
NMS-7083: Show empty string instead of null.
Merge origin/rc/stable/1.14 into jira/NMS-7083
Merge pull request #147 from OpenNMS/jira/NMS-7083

jira/NMS-7083