SwXTextDocument::getTextSelection: fix crash on unsupported mime type

SdXImpressDocument didn't have this problem, FWIW.

Change-Id: Ic88311596b7b92a8e972f366b9e82cca850244f8
(cherry picked from commit 0b532178)

sw/qa/extras/tiledrendering/tiledrendering.cxx

@@ -221,6 +221,9 @@ void SwTiledRenderingTest::testGetTextSelection()
     comphelper::LibreOfficeKit::setActive();
 
     SwXTextDocument* pXTextDocument = createDoc("shape-with-text.fodt");
+    // No crash, just empty output for unexpected mime type.
+    CPPUNIT_ASSERT_EQUAL(OString(), pXTextDocument->getTextSelection("foo/bar"));
+
     SwWrtShell* pWrtShell = pXTextDocument->GetDocShell()->GetWrtShell();
     // Move the cursor into the first word.
     pWrtShell->Right(CRSR_SKIP_CHARS, /*bSelect=*/false, 2, /*bBasicCall=*/false);

sw/source/uibase/uno/unotxdoc.cxx

@@ -3297,6 +3297,9 @@ OString SwXTextDocument::getTextSelection(const char* pMimeType)
     else
         aFlavor.DataType = cppu::UnoType< uno::Sequence<sal_Int8> >::get();
 
+    if (!xTransferable->isDataFlavorSupported(aFlavor))
+        return OString();
+
     uno::Any aAny(xTransferable->getTransferData(aFlavor));
 
     OString aRet;