[Gpsbabel-code] RFC: logLen handling for MTK

[Lorenzo M. C. <lo...@sa...>]

The enclosed patch avoids a segmentation fault on log format change for my 
holux m241 data logger. The crashMe datafile does trigger a segmentation 
fault without the patch.

Since I've been touching common code, I'd be grateful if some kind owner 
of a standard MTK datalogger could try and repeat the crash by changing 
the logformat before applying the diff, and confirm (at least) we don't 
regress after applying it!

If it all works, we'll need to rework the csv output.

Thank you all, yours

 	lorenzo