Index: util/fp2anim
===================================================================
--- util/fp2anim	(revision 251)
+++ util/fp2anim	(revision 252)
@@ -66,10 +66,11 @@
 	ny = -(x2-x1)
 
 	len=sqrt(nx*nx+ny*ny)
-	nx /= len
-	ny /= len
-
-	print "poly", x1+nx*width/2, y1+ny*width/2, x2+nx*width/2, y2+ny*width/2, x2-nx*width/2, y2-ny*width/2, x1-nx*width/2, y1-ny*width/2
+	if (len != 0) {
+		nx /= len
+		ny /= len
+		print "poly", x1+nx*width/2, y1+ny*width/2, x2+nx*width/2, y2+ny*width/2, x2-nx*width/2, y2-ny*width/2, x1-nx*width/2, y1-ny*width/2
+	}
 	if (!omit_ends) {
 		print "fillcircle", x1, y1, width/2, width/10
 		print "fillcircle", x2, y2, width/2, width/10