When I go simulation -> copter on windows - The sitl spits out a json error.

#### Issue details
_Please describe the problem, or desired feature_
When I go simulation -> copter on windows
The sitl spits out this error
Unexpected character encountered while parsing value.
Have
* reinstalled mission planner.
* Ran the same thing on a friend windows computer and it gave the same error.

It looks like there has been a change in the soft in the loop, where is parses some json and someone has changed the json to throw an error.

#### Version
_What version was the issue encountered with_
1.3.74

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

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

#### Hardware type
_What autopilot hardware was used? (pixhawk, pixracer, PX4FMU etc)_
software only

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

Reproduce the simulation → Copter flow on Windows with Mission Planner 1.3.74 and inspect the reported JSON parsing error. Trace which simulation component emits or consumes the malformed value; done means the flow starts without this parsing error and the behavior is verified on Windows.

Written by the indexing model from the issue text.