if someone pastes in an acme window but cancels the paste win will die with 'reading data' error, this patch makes handling of the 'canceled paste' without dying.

Reference: /n/sources/patch/applied/acmewin-paste
Date: Sun Apr 10 06:09:19 CES 2005

--- /acme/bin/source/win/win.c	Sun Apr 10 06:08:14 2005
+++ /acme/bin/source/win/win.c	Sun Apr 10 06:08:12 2005
@@ -183,7 +183,7 @@
 		if(write(w->addr, buf, n) != n)
 			error("error writing addr: %r");
 		n = read(w->data, buf, sizeof buf);
-		if(n <= 0)
+		if(n < 0)
 			error("reading data: %r");
 		nr = nrunes(buf, n);
 		while(m+nr >q1){