[Backdrop] Call onClick regardless of setClosing prop presence

.changeset/unlucky-bags-fry.md

@@ -0,0 +1,5 @@
+---
+'@shopify/polaris': patch
+---
+
+Fixed Backdrop onClick callback when setClosing is missing

polaris-react/src/components/Backdrop/Backdrop.tsx

@@ -30,8 +30,11 @@ export function Backdrop(props: BackdropProps) {
   };
 
   const handleClick = () => {
-    if (setClosing && onClick) {
+    if (setClosing) {
       setClosing(false);
+    }
+
+    if (onClick) {
       onClick();
     }
   };

polaris-react/src/components/Backdrop/tests/Backdrop.test.tsx

@@ -7,9 +7,16 @@ describe('<Backdrop />', () => {
   describe('onClick()', () => {
     it('is called when the backdrop is clicked', () => {
       const spy = jest.fn();
-      const backdrop = mountWithApp(
-        <Backdrop onClick={spy} setClosing={() => {}} />,
-      );
+      const backdrop = mountWithApp(<Backdrop onClick={spy} />);
+      backdrop.find('div')!.trigger('onClick');
+      expect(spy).toHaveBeenCalled();
+    });
+  });
+
+  describe('setClosing()', () => {
+    it('is called when the backdrop is clicked', () => {
+      const spy = jest.fn();
+      const backdrop = mountWithApp(<Backdrop setClosing={spy} />);
       backdrop.find('div')!.trigger('onClick');
       expect(spy).toHaveBeenCalled();
     });