Using Firefox and plain text the interface crashes

If you use Firefox (test with rel. 65 - 64 bit) as a browser and the composition of the emails is configured in plain-text the interface is blocked after having pressed the answer for the second time in an e-mail.

Steps to reproduce:

• access WebTop with Firefox and configure the composition of the plain-text mail
• after reloading the interface, open an email and click on the "Reply" button
• close the email and click the "Reply" button again

Expected behaviour:

• the e-mail opens regularly

Actual behaviour:

• the interface is blocked with the loading in progress and the only way to exit is to do a refresh (F5)