#47 Overlapping Channel Searches cause error

[Rodney Kinney]

This occurs when a Channel Search is initiated and a
second Channel Search is initiated before a ReplyListEnd
is received. After the first search terminates, server
responses to the second channel search will throw a
NullPointerException in Server.onReplyList() because
_search is set to null when a search terminates.

It's much cleaner to disallow overlapping Channel
Searches. The attached replacement to
Server.startChannelSearch solves the problem.

[Rodney Kinney]

Java source for Server.startChannelSearch() method