diff --git a/core/flyout_horizontal.ts b/core/flyout_horizontal.ts
index 372b40c84..b344f41fd 100644
--- a/core/flyout_horizontal.ts
+++ b/core/flyout_horizontal.ts
@@ -267,29 +267,35 @@ export class HorizontalFlyout extends Flyout {
     for (let i = 0, item; (item = contents[i]); i++) {
       if (item.type === 'block') {
         const block = item.block;
-        const allBlocks = block!.getDescendants(false);
+
+        if (block === undefined || block === null) {
+          continue;
+        }
+
+        const allBlocks = block.getDescendants(false);
+
         for (let j = 0, child; (child = allBlocks[j]); j++) {
           // Mark blocks as being inside a flyout.  This is used to detect and
           // prevent the closure of the flyout if the user right-clicks on such
           // a block.
           child.isInFlyout = true;
         }
-        const root = block!.getSvgRoot();
-        const blockHW = block!.getHeightWidth();
+        const root = block.getSvgRoot();
+        const blockHW = block.getHeightWidth();
         // Figure out where to place the block.
-        const tab = block!.outputConnection ? this.tabWidth_ : 0;
+        const tab = block.outputConnection ? this.tabWidth_ : 0;
         let moveX;
         if (this.RTL) {
           moveX = cursorX + blockHW.width;
         } else {
           moveX = cursorX - tab;
         }
-        block!.moveBy(moveX, cursorY);
+        block.moveBy(moveX, cursorY);
 
-        const rect = this.createRect_(block!, moveX, cursorY, blockHW, i);
+        const rect = this.createRect_(block, moveX, cursorY, blockHW, i);
         cursorX += blockHW.width + gaps[i];
 
-        this.addBlockListeners_(root, block!, rect);
+        this.addBlockListeners_(root, block, rect);
       } else if (item.type === 'button') {
         const button = item.button as FlyoutButton;
         this.initFlyoutButton_(button, cursorX, cursorY);