Fix mess with canvas name for HSI

routes/index.mjs

@@ -31,7 +31,8 @@ router.get('/iiif/:manifestid/canvas/:name', async function(req, res) {
 	try {
 		canvas = await generateCanvas(req.params.manifestid, req.params.name)
 	} catch(error) {
-		res.status(500).json({status: 500, message: 'There was an error processing this request'});
+		res.status(500).json({status: 500, message: 'There was an error processing this request: ' + error});
+		return;
 	}
 	res.json(canvas);
 });