being more defensive, in seeing JENKINS-7809 and the following stack trace:

java.lang.NegativeArraySizeException
	at hudson.remoting.ProxyOutputStream$Chunk.<init>(ProxyOutputStream.java:175)
	at hudson.remoting.ProxyOutputStream._write(ProxyOutputStream.java:123)
	at hudson.remoting.ProxyOutputStream.write(ProxyOutputStream.java:103)

remoting/src/main/java/hudson/remoting/PipeWindow.java

@@ -139,7 +139,7 @@ abstract class PipeWindow {
                 if (available>0)
                     return available;
 
-                while (available==0) {
+                while (available<=0) {
                     wait();
                 }
             }