Mission Planner 1.3.6x does not open Logs

#### Issue details
_Please describe the problem, or desired feature_

Since i updated MP on mylap top Build 1.3.6904.12345 (and 2 prvious ones) i cannot open logs any more.
My desktop was not updated stil in 1.3.6877.26630 still works fine it open logs no problems.
I beleive there is a bug in latest version.

#### Version
_What version was the issue encountered with_

#### Platform
[ ] All
[ ] AntennaTracker
[x] Copter
[ ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
_What type of airframe (flying wing, glider, hex, Y6, octa etc)_

#### Hardware type
_What autopilot hardware was used? (pixhawk, pixracer, PX4FMU etc)_
Pixhawk the cube

#### Logs
_Please provide a link to any relevant logs that show the issue_

No source files, tests, or entry points are identified. First reproduce the failure in Mission Planner build 1.3.6904.12345 and compare it with 1.3.6877.26630, using the Copter and Pixhawk Cube setup described; done means Logs opens reliably in the current build.

Written by the indexing model from the issue text.