Handle empty x-values in generic stats

stats.py

@@ -29,7 +29,10 @@ def stats_generic(req, param=None):
 	rows = query(statsqueries[req], *(statsqueries[req].count('?')*[param]))
 	res = {'x':[], 'y':[]}
 	for row in rows:
+		if row['x'] != '':
 			res['x'].append(row['x'])
+		else:
+			res['x'].append('leer')
 		res['y'].append(row['y'])
 	return Response(json.dumps(res, default=plotly_date_handler),  mimetype='application/json')