GPX read errors - manage gracefully

[caver456]

There could be lots of examples of GPX read errors due to invalid GPX file(s). GPSIO should handle them gracefully, and continue to read any other valid file(s) and progress to the import checkbox list normally. The symptom is a red line "GPS Exception: GPX Read error: blahblahblah" in the 'Import From GPS" dialog, with no checkbox chart. Go ahead and document each instance as a comment on this issue, but, the goal is to handle general bad file problems gracefully and give meaningful feedback to the user such as "blah file was bad and ignored (with detailed reason); remaining files were read successfully")

[caver456]

GPS Exception: GPS Read error: "Expected '>', but got ""." File:
"E:/Garmin/GPX/gpsio2017_06_17_113936.gpx" Line: 73
Column: 19

The filename indicates it was a file written by gpsio...

The (presumably) offending lines in the file - note the offending period is actually line 37, column 9, so line and column numbers are not to be trusted (note also that each line ends in ^M - maybe this can be prevented? Apparently not a real problem)

  <trkpt lat="39.308523614305" lon="-120.66604154691"/>
  <trkpt lat="39.308519463608" lon="-120.66604691133"/>
</tr.310454065" lon="-120.668912223"/>
  <trkpt lat="39.310411736" lon="-120.668861512"/>
  <trkpt lat="39.310299587" lon="-120.668799402"/>

gpsio2017_06_17_113936.gpx.txt

[caver456]

Maybe the chunk boundary is at that spot... will do some investigation in the next few days.