fix: default missing horizontal offset

Author: nrps9909

src/Filler.tsx

@@ -61,7 +61,7 @@ const Filler = React.forwardRef(
       innerStyle = {
         ...innerStyle,
         transform: `translateY(${offsetY}px)`,
-        [rtl ? 'marginRight' : 'marginLeft']: -offsetX,
+        [rtl ? 'marginRight' : 'marginLeft']: -(offsetX ?? 0),
         position: 'absolute',
         left: 0,
         right: 0,

tests/filler.test.tsx

@@ -0,0 +1,20 @@
+import { render } from '@testing-library/react';
+import React from 'react';
+import Filler from '../src/Filler';
+
+describe('Filler', () => {
+  it.each([
+    [false, 'marginLeft'],
+    [true, 'marginRight'],
+  ] as const)('defaults an omitted horizontal offset in RTL %s', (rtl, marginProperty) => {
+    const { container } = render(
+      <Filler height={100} offsetY={0} rtl={rtl}>
+        <div>item</div>
+      </Filler>,
+    );
+
+    expect(container.firstElementChild?.firstElementChild).toHaveStyle({
+      [marginProperty]: '0px',
+    });
+  });
+});