tiff handler: ensure valid value of the compression option

Bound the value of the compression setting to the possible values of
the QTiffHandler::Compression enum.

Change-Id: I50e1eb8014654d8b4403d7f06e6099661e57562c
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/plugins/imageformats/tiff/qtiffhandler.cpp

@@ -815,7 +815,7 @@ QVariant QTiffHandler::option(ImageOption option) const
 void QTiffHandler::setOption(ImageOption option, const QVariant &value)
 {
     if (option == CompressionRatio && value.type() == QVariant::Int)
-        d->compression = value.toInt();
+        d->compression = qBound(0, value.toInt(), 1);
     if (option == ImageTransformation) {
         int transformation = value.toInt();
         if (transformation > 0 && transformation < 8)