Fix FTBFS with GCC6

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

src/backgroundmanager.cpp

@@ -258,7 +258,7 @@ TQPixmap* BackgroundManager::preview(const TQString &image)
 
 	if (!entry) {
 ///		std::cout << "BackgroundManager: Requested the preview of an unexisting image: " << image << std::endl;
-		return false;
+		return 0;
 	}
 
 	// The easiest way: already computed:

src/formatimporter.cpp

@@ -197,7 +197,7 @@ TQDomElement FormatImporter::importBasket(const TQString &folderName)
 	disposition.setAttribute("mindMap",     "false");
 	disposition.setAttribute("columnCount", "1");
 	disposition.setAttribute("free",        "false");
-	bool isCheckList = XMLWork::trueOrFalse( XMLWork::getElementText(properties, "showCheckBoxes", false) );
+	bool isCheckList = XMLWork::trueOrFalse( XMLWork::getElementText(properties, "showCheckBoxes", "") );
 
 	// Insert all notes in a group (column): 1/ rename "items" to "group", 2/ add "notes" to root, 3/ move "group" into "notes"
 	TQDomElement column = XMLWork::getElement(docElem, "items");