Crash when parsing multi-cd album

[classical11]

Hi Simon,

I've just added a new 5-CD album, all flac, and MinimServer crashes with this call stack:

java.lang.NullPointerException
at com.minimserver.Server.constructAlbum(Server.java:3792)
at com.minimserver.Server.constructMergedAlbums(Server.java:2634)
at com.minimserver.Server.doStart(Server.java:1467)
at com.minimserver.Server.start(Server.java:382)
at org.jminim.core.ContextImpl.startComponent(ContextImpl.java:156)
at org.jminim.core.ContextImpl.start(ContextImpl.java:84)
at org.jminim.core.RootContextImpl.startComponent(RootContextImpl.java:36)
at org.jminim.core.ContextImpl.start(ContextImpl.java:84)
at org.jminim.core.RuntimeImpl.run(RuntimeImpl.java:398)
at org.jminim.core.LauncherImpl.run(LauncherImpl.java:681)
at org.jminim.core.LauncherImpl.launch(LauncherImpl.java:85)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.jav​a:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.jminim.launch.Launcher.launch(Launcher.java:64)
at com.minimserver.launch.LaunchServer.main(LaunchServer.java:23)
MinimServer error: now stopped, use 'restart' or 'exit'

--------------

If I remove the album, clean up the cache and restart Minim, it works fine, so it's definitely this album.
I'm not sure what's wrong with it though..

There doesn't seem to be anything in the logs (with debug level enabled) that points to this album (the album logged before the exception is not the one that is causing the problem.):

....
....
12:09:45.375 main: album=Piano - Bach Haydn Schumann singleArtist=Alexis Weissenberg - piano
java.lang.NullPointerException
at com.minimserver.Server.constructAlbum(Server.java:3792)
at com.minimserver.Server.constructMergedAlbums(Server.java:2634)
at com.minimserver.Server.doStart(Server.java:1467)
at com.minimserver.Server.start(Server.java:382)
at org.jminim.core.ContextImpl.startComponent(ContextImpl.java:156)
at org.jminim.core.ContextImpl.start(ContextImpl.java:84)
at org.jminim.core.RootContextImpl.startComponent(RootContextImpl.java:36)
at org.jminim.core.ContextImpl.start(ContextImpl.java:84)
at org.jminim.core.RuntimeImpl.run(RuntimeImpl.java:398)
at org.jminim.core.LauncherImpl.run(LauncherImpl.java:681)
at org.jminim.core.LauncherImpl.launch(LauncherImpl.java:85)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.jav​a:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.jminim.launch.Launcher.launch(Launcher.java:64)
at com.minimserver.launch.LaunchServer.main(LaunchServer.java:23)
12:09:45.377 main: exception while starting component minimserver in context context0
12:09:45.377 main: >>> EVENT >>> componentError: minimserver
12:09:45.377 main: ServerControl: componentError event for minimserver
MinimServer error: now stopped, use 'restart' or 'exit'
12:09:45.377 main: Monitor: componentError event for minimserver in context context0
12:09:45.377 main: stopping component minimserver in context context0
12:09:45.377 main: >>> EVENT >>> componentStopping: minimserver
12:09:45.377 main: ServerControl: componentStopping event for minimserver
12:09:45.377 main: Monitor: componentStopping event for minimserver in context context0
12:09:45.377 main: stopping MinimServer
12:09:45.378 main: disposing http service
12:09:45.378 main: disposing HTTPContext
12:09:45.378 main: removing contextRoot minimserver
12:09:45.378 main: HTTPService: removing path minimserver
12:09:45.378 main: HTTPService: found handler for minimserver
12:09:45.378 main: HTTPService: closing server socket
12:09:45.378 main: http service disposed
12:09:45.378 main: closing cacheData[0]
12:09:45.378 main: cacheData[0] closed
12:09:45.378 main: stopped MinimServer
12:09:45.378 main: stopped component minimserver in context context0
12:09:45.378 main: >>> EVENT >>> componentStopped: minimserver
12:09:45.378 main: ServerControl: componentStopped event for minimserver
12:09:45.378 main: Monitor: componentStopped event for minimserver in context context0
12:09:45.378 main: error while starting context context0
12:09:45.378 main: stopping context context0
12:09:45.378 main: >>> EVENT >>> contextStopping: context0
12:09:45.378 main: ServerControl: contextStopping event for context0
12:09:45.378 Thread-7: HTTPService: server socket accept exception: Socket closed
12:09:45.378 Thread-7: HTTPService: exiting server thread Thread[Thread-7,5,main]
12:09:45.378 main: Monitor: contextStopping event for context0
12:09:45.378 main: stopping component minimserver in context context0
12:09:45.378 main: >>> EVENT >>> componentStopping: minimserver
12:09:45.378 main: ServerControl: componentStopping event for minimserver
12:09:45.378 main: Monitor: componentStopping event for minimserver in context context0
12:09:45.378 main: stopping MinimServer
12:09:45.378 main: closing cacheData[0]
12:09:45.378 main: cacheData[0] closed
12:09:45.378 main: stopped MinimServer
12:09:45.378 main: stopped component minimserver in context context0
12:09:45.378 main: >>> EVENT >>> componentStopped: minimserver
12:09:45.378 main: ServerControl: componentStopped event for minimserver
12:09:45.378 main: Monitor: componentStopped event for minimserver in context context0
12:09:45.378 main: stopped context context0
12:09:45.378 main: >>> EVENT >>> contextStopped: context0
12:09:45.378 main: ServerControl: contextStopped event for context0
12:09:45.378 main: Monitor: contextStopped event for context0
12:09:45.378 main: error while starting context rootContext
12:09:45.378 main: >>> EVENT >>> startupComplete
12:09:45.378 main: ServerControl: startupComplete event
12:09:45.378 main: Monitor: startupComplete event