Compile Error message when graphing tlog from antenna tracker

From MP's Flight Data, Telemetry Log tab, pressed "Tlog > Graph", then pressed "Graph Log" and although a graph did appear, a message saying "Compile error" also appeared.

[2016-05-28 11-45-03.zip](https://github.com/ArduPilot/MissionPlanner/files/287542/2016-05-28.11-45-03.zip)

Reproduce the issue in Mission Planner from Flight Data's Telemetry Log tab using the attached 2016-05-28 log, then choose Tlog > Graph and press Graph Log. Confirm whether the graph still appears alongside the "Compile error" message; the issue does not identify a source file or test for further investigation.

Written by the indexing model from the issue text.