applyDelta deletes wrong text with insert + delete

[luin]

In applyDelta, if a block embed is inserted to the middle of a line, the implicitly added \n cause the deletion happens at a wrong position.

Steps for Reproduction

The following test case fails:

    it('deletes text and appends block embed', function() {
      const editor = this.initialize(Editor, `<p><br></p><p>abc</p>`);
      editor.applyDelta(
        new Delta()
          .retain(2)
          .insert({ video: '#' })
          .delete(2),
      );
      expect(this.container).toEqualHTML(
        '<p><br></p><p>a</p><iframe class="ql-video" frameborder="0" allowfullscreen="true" src="#"></iframe><p><br></p>',
      );
    });

Expected behavior:

The result is <p><br></p><p>a</p><iframe class="ql-video" frameborder="0" allowfullscreen="true" src="#"></iframe><p><br></p>.

Actual behavior:

The result is <p><br></p><p>a</p><p>c</p>

Platforms:

Chrome v103.

Version:

2.0.0-dev.4