Fix emission of QQuickPaddedRectangle::topPaddingChanged

...when setting the padding property.

The topPaddingChanged signal is to be emitted if padding changed and no
separate topPadding has been specified.  Unlike the
other *PaddingChanged signals, it was emitted if topPadding *was*
specified.

Fixes: QTBUG-104865
Pick-to: 6.2 6.3 6.4
Change-Id: I8585c4b3f7aa70030b5c6e195516e1aba73e5c46
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

src/quickcontrols2impl/qquickpaddedrectangle.cpp

@@ -23,7 +23,7 @@ void QQuickPaddedRectangle::setPadding(qreal padding)
         m_padding = padding;
         update();
         emit paddingChanged();
-        if (m_hasTopPadding)
+        if (!m_hasTopPadding)
             emit topPaddingChanged();
         if (!m_hasLeftPadding)
             emit leftPaddingChanged();