Sorry for my wrong comment #14 (due to my mix of Java versions and the different options how to start the IDE)
the version from today has the fix for App.open() for Java8. later today I will make a new build, that also fixes this for Java 7.
I recommend to go back to Java 8, no need to stick with Java 7.
For other workarounds see the bug mentioned in comment #11
Sorry for my wrong comment #14 (due to my mix of Java versions and the different options how to start the IDE)
the version from today has the fix for App.open() for Java8.
later today I will make a new build, that also fixes this for Java 7.
I recommend to go back to Java 8, no need to stick with Java 7.
For other workarounds see the bug mentioned in comment #11