Mutators of shadow block lists_create_with creates extra shadow block

Problem statement

TODO…

Expected Behavior

An empty socket should appear where the new socket was created.

Actual Behavior

Steps to Reproduce

Add this to the blockly playground. Add a mutator between 2 and 3. A 3 shadow block appears both in the new socket and on the workspace

<xml xmlns="http://www.w3.org/1999/xhtml">
  <block type="lists_isEmpty" id="lUo%hD1:H)4+qIGwduxZ" x="113" y="213">
    <value name="VALUE">
      <shadow type="lists_create_with" id="McTQO_+6S`Iv,ZCC%$$g">
        <mutation items="3"></mutation>
        <value name="ADD0">
          <shadow type="math_number" id="7eym=to%}T8dnGV^zCix">
            <field name="NUM">1</field>
          </shadow>
        </value>
        <value name="ADD1">
          <shadow type="math_number" id="sVBui$corF3h0`9!e6jz">
            <field name="NUM">2</field>
          </shadow>
        </value>
        <value name="ADD2">
          <shadow type="math_number" id="q+gA9N/,:Xk?eo.:7R3N">
            <field name="NUM">3</field>
          </shadow>
        </value>
      </shadow>
    </value>
  </block>
</xml>

1. Start by…
2. Next, do…

Stack Traces

Replace with error stack trace.

None

Operating System and Browser

Additional Information

[rachel-fenichel]

Usually this means that there’s a shadow DOM on an input that we’re trying to clear out, so it just keeps respawning. The solution is usually to clear out the shadow DOM, then manipulate (add, remove, whatever) the inputs, then add back the shadow DOM.

[plh2]

so what mean by ADD0, ADD1, ADD2

Ignoring non-existent input ADD0 in block lists_create_with