Remove undocumented support for passing no node

Author: wooorm

Diff for: lib/index.js

@@ -40,8 +40,7 @@ import {webNamespaces} from 'web-namespaces'
  *   Equivalent hast node.
  */
 export function fromDom(tree, options) {
-  const result = tree ? transform(tree, options || {}) : undefined
-  return result || {type: 'root', children: []}
+  return transform(tree, options || {}) || {type: 'root', children: []}
 }
 
 /**

Diff for: test/index.js

@@ -123,15 +123,6 @@ test('fromDom', async function (t) {
     assert.deepEqual(fromDom(frag), {type: 'root', children: []})
   })
 
-  await t.test('should handle a missing DOM tree', async function () {
-    assert.deepEqual(
-      // To do: remove.
-      // @ts-expect-error runtime.
-      fromDom(),
-      {type: 'root', children: []}
-    )
-  })
-
   await t.test('should support a text w/o value', async function () {
     assert.deepEqual(fromDom(document.createTextNode('')), {
       type: 'text',