Gtk: Crash on exit when running JavaFX applet in browser

To reproduce this, make sure you are running the SW pipeline (either by running on a system that doesn't support Prism or by removing libprism-es2.so). Then:

1) Download the latest JDK 7u6 / FX cobundle for Linux

2) Setup your plugins directory to point to it:

    mkdir ~/.mozilla/plugins
    cd ~/.mozilla/plugins
    ln -s ..../jre1.7.0_06/lib/i386/libnpjp2.so .

3) Launch firefox (setting the following debug env vars will help)

    export JPI_PLUGIN2_DEBUG=true
    export JPI_PLUGIN2_VERBOSE=true
    firefox

4) Load the following URL:

http://jfx.us.oracle.com/hudson/job/2.2-graphics-scrum/label=windows-i586-14/lastSuccessfulBuild/artifact/artifacts/deployed/DefaultSignedApp/SignedFish.html

(you can use "linux" instead of "windows" it doesn't matter since the samples are platform-independent)