[improvement] Hide translation panel when text no more selected

[mattia-b89]

I think would be an improvement (not a proper bug...) if translation panel would be hided when the source text (the one who invoked the panel) is no more selected.

I run into case, twice:

1. in an input box, when I select a portion of text in order to replace it with a new input, translation panel stays there even after I edit the source text
2. I select text, then I reload the page but translation panel stays there

[jabalv]

1. I can confirm that this would be nice improvement!
2. I was not able to replicate this one!