[CommonHTML] [Firefox] Anomaly with spacing before and after \text

The issue can be seen in https://cdi2tp.math.tecnico.ulisboa.pt/texto/10 with Firefox 52 on Linux Mint. This may be very browser, version, OS,..., specific problem. Absent from Firefox 51 on Windows or Firefox 52 on Android.

Spacing after the phrase "Existe um caminho unindo" in a displayed formula has disappeared although you can see it on mouseover.