From 112f48592f28879212f05c56869e5f6c3337a4ac Mon Sep 17 00:00:00 2001
From: Rachel Fenichel <fenichel@google.com>
Date: Thu, 5 Apr 2018 18:19:56 -0700
Subject: [PATCH] Return early if there's no block

---
 core/workspace_svg.js | 79 ++++++++++++++++++++++---------------------
 1 file changed, 41 insertions(+), 38 deletions(-)

diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index f534ce45a..d74586c31 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -1508,46 +1508,49 @@ Blockly.WorkspaceSvg.prototype.centerOnBlock = function(id) {
     console.warn('Tried to scroll a non-scrollable workspace.');
     return;
   }
+
   var block = this.getBlockById(id);
-  if (block) {
-    // XY is in workspace coordinates.
-    var xy = block.getRelativeToSurfaceXY();
-    // Height/width is in workspace units.
-    var heightWidth = block.getHeightWidth();
-
-    // Find the enter of the block in workspace units.
-    var blockCenterY = xy.y + heightWidth.height / 2;
-
-    // In RTL the block's position is the top right of the block, not top left.
-    var multiplier = this.RTL ? -1 : 1;
-    var blockCenterX = xy.x + (multiplier * heightWidth.width / 2);
-
-    // Workspace scale, used to convert from workspace coordinates to pixels.
-    var scale = this.scale;
-
-    // Center in pixels.  0, 0 is at the workspace origin.  These numbers may
-    // be negative.
-    var pixelX = blockCenterX * scale;
-    var pixelY = blockCenterY * scale;
-
-    var metrics = this.getMetrics();
-
-    // Scrolling to here would put the block in the top-left corner of the
-    // visible workspace.
-    var scrollToBlockX = pixelX - metrics.contentLeft;
-    var scrollToBlockY = pixelY - metrics.contentTop;
-
-    // viewHeight and viewWidth are in pixels.
-    var halfViewWidth = metrics.viewWidth / 2;
-    var halfViewHeight = metrics.viewHeight / 2;
-
-    // Put the block in the center of the visible workspace instead.
-    var scrollToCenterX = scrollToBlockX - halfViewWidth;
-    var scrollToCenterY = scrollToBlockY - halfViewHeight;
-
-    Blockly.hideChaff();
-    this.scrollbar.set(scrollToCenterX, scrollToCenterY);
+  if (!block) {
+    return;
   }
+
+  // XY is in workspace coordinates.
+  var xy = block.getRelativeToSurfaceXY();
+  // Height/width is in workspace units.
+  var heightWidth = block.getHeightWidth();
+
+  // Find the enter of the block in workspace units.
+  var blockCenterY = xy.y + heightWidth.height / 2;
+
+  // In RTL the block's position is the top right of the block, not top left.
+  var multiplier = this.RTL ? -1 : 1;
+  var blockCenterX = xy.x + (multiplier * heightWidth.width / 2);
+
+  // Workspace scale, used to convert from workspace coordinates to pixels.
+  var scale = this.scale;
+
+  // Center in pixels.  0, 0 is at the workspace origin.  These numbers may
+  // be negative.
+  var pixelX = blockCenterX * scale;
+  var pixelY = blockCenterY * scale;
+
+  var metrics = this.getMetrics();
+
+  // Scrolling to here would put the block in the top-left corner of the
+  // visible workspace.
+  var scrollToBlockX = pixelX - metrics.contentLeft;
+  var scrollToBlockY = pixelY - metrics.contentTop;
+
+  // viewHeight and viewWidth are in pixels.
+  var halfViewWidth = metrics.viewWidth / 2;
+  var halfViewHeight = metrics.viewHeight / 2;
+
+  // Put the block in the center of the visible workspace instead.
+  var scrollToCenterX = scrollToBlockX - halfViewWidth;
+  var scrollToCenterY = scrollToBlockY - halfViewHeight;
+
+  Blockly.hideChaff();
+  this.scrollbar.set(scrollToCenterX, scrollToCenterY);
 };
 
 /**