[melodic] RViz panels don't always show at startup

[seanyen]

Problem

Sometimes, after RViz starts up, some panels are not showing, even when I toggle through menu > panels > xyz. On Windows, the repro rate is high, like once out of 5 ~ 10 runs. On Ubuntu, we also observe the same symptom (but with a much lower reproduce rate).

The workaround is to enter\exit fullscreen to refresh the visibility states.

This is also reported on https://answers.ros.org/question/315664/ros-not-running-well-on-windows-10/.

Analysis & Solution

After live debugging, I noticed sometimes forced_hidden_ are not zero at start up. And it turned out forced_hidden_ was not zero-initialized in constructor and it could be anything left from the memory, so it messed up with the later visibility logic.

The solution is to simply initialize it.

[rhaschke]

Thank you very much for tracking down this annoying bug.