Ensure captureOwnerStack returns when no stack is available

Author: eps1lon

packages/react-reconciler/src/ReactCurrentFiber.js

@@ -72,7 +72,7 @@ export function runWithFiberInDEV<A0, A1, A2, A3, A4, T>(
       }
       return callback(arg0, arg1, arg2, arg3, arg4);
     } finally {
-      current = previousFiber;
+      setCurrentFiber(previousFiber);
     }
   }
   // These errors should never make it into a build so we don't need to encode them in codes.json

packages/react-reconciler/src/__tests__/ReactOwnerStacks-test.js

@@ -62,4 +62,14 @@ describe('ReactOwnerStacks', () => {
       '\n    in Bar (at **)' + '\n    in Foo (at **)',
     );
   });
+
+  it('returns null outside of render', async () => {
+    expect(React.captureOwnerStack()).toBe(null);
+
+    await act(() => {
+      ReactNoop.render(<div></div>);
+    });
+
+    expect(React.captureOwnerStack()).toBe(null);
+  });
 });