Target language not available after duplicate tab

[martinpopel]

Steps to reproduce:

1. Select English as the source language. Czech will be automatically selected as the Target.
2. Click "Duplicate tab" in your browser.
3. The Source will remain English, but there is no way how to select Czech as the target - it is not in the drop-down menu. In Chrome the Target is empty, in Firefox it is English.
4. Once you edit the source text, the translation fails - the translation box is red with a message "Translation failed: error
   NOT FOUND".
5. Workaround: You have to change the source language another language and then back to English, so that the target language gets updated to Czech and a translation is shown.

This is not a high-priority issue (though the Duplicate tab trick is useful when studying the effect of slight variations of the input text).