Move thumbnail QSaveFile to correct scope

The QSaveFile is only needed if there is thumbnail creator for the
format of the current file.

thumbnail/thumbnail.cpp

@@ -679,29 +679,26 @@ bool ThumbnailProtocol::createSubThumbnail(QImage& thumbnail, const QString& fil
         if (thumbnail.isNull()) {
             // no cached version is available, a new thumbnail must be created
 
-            QSaveFile thumbnailfile(thumbPath.absoluteFilePath(thumbName));
-            bool savedCorrectly = false;
             ThumbCreator* subCreator = getSubCreator();
             if (subCreator && subCreator->create(filePath, cacheSize, cacheSize, thumbnail)) {
                 scaleDownImage(thumbnail, cacheSize, cacheSize);
 
                 // The thumbnail has been created successfully. Store the thumbnail
                 // to the cache for future access.
+                QSaveFile thumbnailfile(thumbPath.absoluteFilePath(thumbName));
                 if (thumbnailfile.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
                     QFileInfo fi(filePath);
                     thumbnail.setText(QStringLiteral("Thumb::URI"), QString::fromUtf8(fileUrl));
                     thumbnail.setText(QStringLiteral("Thumb::MTime"), QString::number(fi.lastModified().toSecsSinceEpoch()));
                     thumbnail.setText(QStringLiteral("Thumb::Size"), QString::number(fi.size()));
 
-                    savedCorrectly = thumbnail.save(&thumbnailfile, "PNG");
+                    if (thumbnail.save(&thumbnailfile, "png")) {
+                        thumbnailfile.commit();
+                    }
                 }
             } else {
                 return false;
             }
-            if(savedCorrectly)
-            {
-                thumbnailfile.commit();
-            }
         }
     } else {
         ThumbCreator* subCreator = getSubCreator();