FileLocation unusable after close() — stream/channel not nulled

[elharo]

Bug #4

FileLocation.java lines 55-71, 115-122

close() closes the FileChannel and FileInputStream but does not set the channel and stream fields to null. After close(), calling read() calls open() which checks if (stream == null) — but since stream is still non-null (just closed), the re-initialization is skipped and channel.read(buffer) is called on a closed channel, throwing ClosedChannelException.

Fix: set channel = null and stream = null after closing them.