acme: allow :6 in 5-line file

R=rsc
https://codereview.appspot.com/12162043
diff --git a/src/cmd/acme/addr.c b/src/cmd/acme/addr.c
index e7843cd..f09688d 100644
--- a/src/cmd/acme/addr.c
+++ b/src/cmd/acme/addr.c
@@ -77,6 +77,8 @@
 			if(textreadc(t, q1++) == '\n' || q1==t->file->b.nc)
 				if(--line > 0)
 					q0 = q1;
+		if(line==1 && q1==t->file->b.nc) // 6 goes to end of 5-line file
+			break;
 		if(line > 0)
 			goto Rescue;
 		break;