Load additional views throws an error if the /misc/views dir doesn't exist

[K-Meech]

To reproduce:

• Open Platybrowser
• Right click in viewer and select 'Load Additional Views'
• Load from 'Current project'

Error thrown:

java.lang.RuntimeException
Exception in thread "Thread-32" java.lang.RuntimeException: java.lang.RuntimeException
	at org.embl.mobie.io.github.RESTCaller.get(RESTCaller.java:102)
	at org.embl.mobie.io.github.GitHubContentGetter.getContent(GitHubContentGetter.java:66)
	at org.embl.mobie.io.github.GitHubUtils.getFilePaths(GitHubUtils.java:98)
	at org.embl.mobie.io.github.GitHubUtils.getFileNames(GitHubUtils.java:92)
	at org.embl.mobie.io.util.IOHelper.getFileNames(IOHelper.java:336)
	at org.embl.mobie.ui.UserInterfaceHelper.selectPathFromProject(UserInterfaceHelper.java:238)
	at org.embl.mobie.lib.view.AdditionalViewsLoader.lambda$loadAdditionalViewsDialog$0(AdditionalViewsLoader.java:59)
	at java.lang.Thread.run(Thread.java:750)
Caused by: java.lang.RuntimeException
	at org.embl.mobie.io.github.RESTCaller.parseResponse(RESTCaller.java:113)
	at org.embl.mobie.io.github.RESTCaller.get(RESTCaller.java:99)
	... 7 more

An additional check is needed that /misc/views exists and there is at least one json file inside of it. Otherwise, show a message that no additional views are available, or don't show the 'current project' option at the start.