Demo not works correctly on Firefox (51.0.1, Windows)

[ratuka]

Error message on the console:
SEVERE: Possible problem with your *.gwt.xml module file.
The compile time user.agent value (safari) does not match the runtime user.agent value (gecko1_8).
Expect more errors.
com.google.gwt.useragent.client.UserAgentAsserter$UserAgentAssertionError: Possible problem with your *.gwt.xml module file.
The compile time user.agent value (safari) does not match the runtime user.agent value (gecko1_8).
Expect more errors.