title: Table with margins attribute as list item throws exception ClassCastException
body: <p>I am using</p>
  <pre><code>org.docx4j.convert.in.xhtml.XHTMLImporterImpl
  </code></pre>
  <p>And when I call convert(html, &quot;&quot;); with following html:</p>
  <pre><code>&lt;ul&gt;
      &lt;li&gt;first list item&lt;/li&gt;
      &lt;li&gt;
          &lt;table style=&quot;margin-left: auto; margin-right: auto; width: 75%; table-layout: fixed;&quot;&gt;
              &lt;tbody&gt;
              &lt;tr&gt;
                  &lt;td&gt;
                      &lt;p&gt;ROW&lt;/p&gt;
                  &lt;/td&gt;
              &lt;/tr&gt;
              &lt;/tbody&gt;
          &lt;/table&gt;
      &lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  <p>I get the following stack trace:</p>
  <pre><code>    java.lang.ClassCastException: class org.docx4j.org.xhtmlrenderer.css.constants.IdentValue cannot be cast to class org.docx4j.org.xhtmlrenderer.css.style.derived.LengthValue (org.docx4j.org.xhtmlrenderer.css.constants.IdentValue and org.docx4j.org.xhtmlrenderer.css.style.derived.LengthValue are in unnamed module of loader 'app')
      at org.docx4j.convert.in.xhtml.ListHelper.getAbsoluteIndent(ListHelper.java:381)
      at org.docx4j.convert.in.xhtml.TableHelper.setupTblPr(TableHelper.java:120)
      at org.docx4j.convert.in.xhtml.XHTMLImporterImpl.traverse(XHTMLImporterImpl.java:1020)
      at org.docx4j.convert.in.xhtml.XHTMLImporterImpl.traverse(XHTMLImporterImpl.java:1284)
      at org.docx4j.convert.in.xhtml.XHTMLImporterImpl.traverse(XHTMLImporterImpl.java:1284)
      at org.docx4j.convert.in.xhtml.XHTMLImporterImpl.traverse(XHTMLImporterImpl.java:1284)
      at org.docx4j.convert.in.xhtml.XHTMLImporterImpl.traverse(XHTMLImporterImpl.java:1284)
      at org.docx4j.convert.in.xhtml.XHTMLImporterImpl.traverse(XHTMLImporterImpl.java:825)
      at org.docx4j.convert.in.xhtml.XHTMLImporterImpl.convert(XHTMLImporterImpl.java:698)
  </code></pre>
  <p>I can tell that it is caused by margin-left and margin-right in the style attribute for the table because if I remove those convert() doesn't thrown an exception.
  Does anyone know any workaround for this that doesn't involve removing margins from the table?</p>