Network sometimes disintegrate

[marimeireles]

I don't know what triggers it, according to @ianhi the culprit might be: https://github.com/QuantStack/ipycytoscape/pull/109/files#r498907209

Here's a screenshot of what's going on:

https://user-images.githubusercontent.com/17600982/94941256-296c5a00-04c4-11eb-8084-4bc818918aff.png