Fix missing check for empty array in breadcrumbs

Co-Authored-By: Kyle Durand <kyledurand@users.noreply.github.com>

Author: itwasmattgregg

.changeset/twelve-grapes-reply.md

@@ -2,4 +2,4 @@
 '@shopify/polaris': minor
 ---
 
-Adds the ability for breadcrumbs to be passed as a singular object instead of an array to allow support for upcoming v11 changes
+Added the ability for breadcrumbs to be passed as a singular object instead of an array to allow support for upcoming v11 changes

polaris-react/src/components/Page/components/Header/Header.tsx

@@ -98,7 +98,8 @@ export function Header({
     !actionGroups.length;
 
   const breadcrumbMarkup =
-    (Array.isArray(breadcrumbs) && breadcrumbs.length > 0) || breadcrumbs ? (
+    (Array.isArray(breadcrumbs) && breadcrumbs.length > 0) ||
+    (!Array.isArray(breadcrumbs) && breadcrumbs) ? (
       <div className={styles.BreadcrumbWrapper}>
         <Breadcrumbs breadcrumbs={breadcrumbs} />
       </div>