may not return uninitialized Completion structure.  also
do not return nil if directory is empty.  this was inspired
by bitbucket issue #139 by Mauricio CA
	https://bitbucket.org/rsc/plan9port/issue/139/bogus-error-message-when-using-control-f
but i think the fix on bitbucket will return uninitialized memory.
also, it does a bunch of dancing around in acme, which doesn't
seem interesting.  other opinions?

Reference: /n/atom/patch/applied/completenildir
Date: Wed Jan  8 13:12:05 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/libcomplete/complete.c	Wed Jan  8 13:08:29 2014
+++ /sys/src/libcomplete/complete.c	Wed Jan  8 13:08:30 2014
@@ -58,7 +58,7 @@
 		return nil;
 
 	n = dirreadall(fd, &dirp);
-	if(n <= 0){
+	if(n < 0){
 		close(fd);
 		return nil;
 	}
@@ -73,10 +73,9 @@
 
 	name = malloc(n*sizeof(char*));
 	mode = malloc(n*sizeof(ulong));
-	c = malloc(sizeof(Completion) + len);
+	c = mallocz(sizeof(Completion) + len, 1);
 	if(name == nil || mode == nil || c == nil)
 		goto Return;
-	memset(c, 0, sizeof(Completion));
 
 	/* find the matches */
 	len = strlen(s);