fix java.nio.file.FileSystemNotFoundException and reorganize code

[springzfx]

If you run the jar file ouside IDE, then an error will be reprted:

[JavaFX Application Thread] ERROR org.jabref.JabRefMain - Unexpected exception
java.nio.file.FileSystemNotFoundException: null
at com.sun.nio.zipfs.ZipFileSystemProvider.getFileSystem(ZipFileSystemProvider.java:171) ~[zipfs.jar:1.8.0_172]
at com.sun.nio.zipfs.ZipFileSystemProvider.getPath(ZipFileSystemProvider.java:157) ~[zipfs.jar:1.8.0_172]
at java.nio.file.Paths.get(Paths.java:143) ~[?:1.8.0_172]
at org.jabref.gui.util.ThemeLoader.(ThemeLoader.java:52) ~[JabRef--master--latest.jar:?]
at org.jabref.Globals.startBackgroundTasks(Globals.java:82) ~[JabRef--master--latest.jar:?]
at org.jabref.JabRefMain.start(JabRefMain.java:63) ~[JabRef--master--latest.jar:?]
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863) ~[jfxrt.jar:?]
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326) ~[jfxrt.jar:?]
at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295) ~[jfxrt.jar:?]
at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_172]
at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294) ~[jfxrt.jar:?]
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95) ~[jfxrt.jar:?]
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method) ~[jfxrt.jar:?]
at com.sun.glass.ui.gtk.GtkApplication.lambda$null$48(GtkApplication.java:139) ~[jfxrt.jar:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_172]

It is just an url problem, simple to fix. I added some logs, and reorganized a little code.

---

• Change in CHANGELOG.md described
• Tests created for changes
• Manually tested changed features in running JabRef
• Screenshots added in PR description (for bigger UI changes)
• Ensured that the git commit message is a good one
• Check documentation status (Issue created for outdated help page at help.jabref.org?)

[Siedlerchr]

Thanks, I noticed that the independent jar would not start

[Siedlerchr]

Please fix the checkstyle issues from travis and we can mergei t.

[tobiasdiez]

LGTM. Thanks for you contribution!

[springzfx]

In travis, I get this, what should I do:

Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0. Use '--warning-mode all' to show the individual deprecation warnings. See https://docs.gradle.org/4.10.2/userguide/command_line_interface.html#sec:command_line_warnings

[Siedlerchr]

You can ignore the other warning about gradle. But you should check the checkstyle output

[springzfx]

yes, I have fixed the checkstyle issue.

[tobiasdiez]

The gui tests seems to have been crashed, as they sometimes do. I'll merge now and hope it still works on master.