sd theme: fix applying new colors after theme change for group shapes

UpdateSdrObject() is called for both group and non-group shapes, so
don't assume that they always have text, otherwise we would crash.

Change-Id: I3672673176f0cb462a8b8d61a68466f541e9ce06
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128248
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

svx/qa/unit/styles.cxx

@@ -68,6 +68,7 @@ CPPUNIT_TEST_FIXTURE(Test, testThemeChange)
     OUString aURL = m_directories.getURLFromSrc(DATA_DIRECTORY) + "theme.pptx";
     getComponent() = loadFromDesktop(aURL);
     uno::Reference<drawing::XDrawPagesSupplier> xDrawPagesSupplier(getComponent(), uno::UNO_QUERY);
+    // The draw page also contains a group shape to make sure we don't crash on group shapes.
     uno::Reference<drawing::XMasterPageTarget> xDrawPage(
         xDrawPagesSupplier->getDrawPages()->getByIndex(0), uno::UNO_QUERY);
     uno::Reference<drawing::XShapes> xDrawPageShapes(xDrawPage, uno::UNO_QUERY);

svx/source/styles/ColorSets.cxx

@@ -74,6 +74,12 @@ void UpdateSdrObject(svx::Theme* pTheme, SdrObject* pObject)
     }
 
     uno::Reference<text::XTextRange> xShape(pObject->getUnoShape(), uno::UNO_QUERY);
+    if (!xShape.is())
+    {
+        // E.g. group shapes have no text.
+        return;
+    }
+
     uno::Reference<container::XEnumerationAccess> xText(xShape->getText(), uno::UNO_QUERY);
     uno::Reference<container::XEnumeration> xParagraphs = xText->createEnumeration();
     while (xParagraphs->hasMoreElements())