When running the server in a CLI (ie. "java -jar minecraft_server.jar nogui"), on the server console, pressing spacebar and hitting enter causes the server to crash with ArrayOutOfBoundsException. The issue occurs regardless of whether a single space or multiple spaces are entered.
The crash log is attached.
Confirmed. When tested, the server "appeared" to continue functioning ie client was able to continue placing blocks etc, but when the client disconnected, the server was unable to be logged back into.
Once the server was restarted it was clear the placed blocks hadn't been saved.