title: Changing theme attribute when usage
body: <p>I created <code>popupMenuTheme</code>. I need to use it twice. The first one is typical of the theme, and the second has a little difference of <code>fontWeight</code>, so I need to inherit all properties but the <code>fontWeight</code> attribute, but when I do so the popup menu converted into a white container.</p>
  <p>Theme code:</p>
  <pre><code> popupMenuTheme: theme.popupMenuTheme.copyWith(
                  color: const Color(pagesBackgroundColor),
                  elevation: 3,
                  textStyle: TextStyle(
                    color: const Color(accentColor),
                    fontFamily:
                        Localizations.localeOf(context).languageCode == 'ar'
                            ? 'almasry'
                            : 'patrick',
                    fontSize: 3.5.h,
                    fontWeight: FontWeight.w700,
                  ),
                ),
  </code></pre>
  <p>Updated theme code:</p>
  <pre><code>Theme(
    data: Theme.of(context).copyWith(
      popupMenuTheme:const PopupMenuThemeData(
        textStyle: TextStyle(
      fontWeight: FontWeight.w900,
    ))),
    child: PopupMenuButton(
      itemBuilder: (context) =&gt; const [
        PopupMenuItem(child: Text(&quot;update&quot;)),
        PopupMenuItem(child: Text(&quot;delete&quot;)),
      ],
      icon: const Icon(
        Icons.more_vert,
        color: Color(accentColor),
      ),
    ),
  ),
  </code></pre>