Fixed error that would crash host application if memcached server went away.

lib/memcache.js

@@ -28,6 +28,7 @@ var tcp = require('net'),
 
 var crlf = "\r\n";
 var crlf_len = crlf.length;
+var self;
 
 var error_replies = ['ERROR', 'NOT_FOUND', 'CLIENT_ERROR', 'SERVER_ERROR'];
 
@@ -47,7 +48,7 @@ util.inherits(Client, process.EventEmitter);
 Client.prototype.connect = function () {
 	if (!this.conn) {
 	    this.conn = new tcp.createConnection(this.port, this.host);
-		var self = this;
+		self = this;
 	    this.conn.addListener("connect", function () {
 	        this.setTimeout(0);          // try to stay connected.
 	        this.setNoDelay();
@@ -107,7 +108,12 @@ Client.prototype.dispatchHandles = function() {
 Client.prototype.query = function(query, type, callback) {
 	this.callbacks.push({ type: type, fun: callback });
 	this.sends++;
-	this.conn.write(query + crlf);
+	if (this.conn !== null) {
+		this.conn.write(query + crlf);
+	} else {
+		// Server has crashed or in another way become unavailable, connection closed.
+		self.emit("close");
+	}
 };
 
 Client.prototype.close = function() {