Yellow box warning about more than one navigators

[agazso]

There is a yellowbox warning every time when starting the app in debug mode. It's annoying to when testing and I don't want to suppress it because there may be a real issue behind it.

https://reactnavigation.org/docs/en/common-mistakes.html#explicitly-rendering-more-than-one-navigator

[agazso]

See this https://github.com/felfele/felfele/pull/422