TypeError when voting too rapidly

[lgelauff]

Testing on montage-dev

Reproduce:

• have a round active with several open images that you're jury member on
• use your keyboard shortcuts to vote rapidly by rapidly pressing the buttons until you voted 5 times. (e.g. 1/2/3/4/5 in rating, or up/down in yes/no) No problem.
• Use your mouse to vote by clicking rapidly by clicking 3 times successively on the same spot (up/down thumb or a star). This gives a typeError in console and gives the user a continuous 'waiting' message.
• keyboard shortcuts still work. Mouseclicks are disabled until page is reloaded.

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