From 14b6fdd51eaac14671b1cbd17f69f6cda846557e Mon Sep 17 00:00:00 2001
From: Evert Timberg <evert.timberg@gmail.com>
Date: Wed, 11 Nov 2015 21:40:29 -0500
Subject: [PATCH] Bail out, same as the x axis

---
 src/core/core.scale.js | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/core/core.scale.js b/src/core/core.scale.js
index edf807de0..f40f6fa2d 100644
--- a/src/core/core.scale.js
+++ b/src/core/core.scale.js
@@ -467,6 +467,11 @@
 					var xTickEnd = this.options.position == "right" ? this.left + 5 : this.right;
 
 					helpers.each(this.ticks, function(label, index) {
+						// If the callback returned a null or undefined value, do not draw this line
+						if (label === undefined || label === null) {
+							return;
+						}
+
 						var yLineValue = this.getPixelForTick(index); // xvalues for grid lines
 
 						if (this.options.gridLines.show) {