Fix genre chart if no viewers

src/facilities/studio/studioCharts.js

@@ -97,7 +97,7 @@ App.Porn.makeFameProgressChart = function(slave) {
 App.Porn.makeViewershipChart = function(slave) {
 	const container = document.createElement("div");
 
-	const data = {name: "Total viewership", children: []};
+	const data = {name: "Total viewership", children: [], value:0};
 	for (const type of Object.values(App.Porn.GenreType)) {
 		const child = {name: type, children: []};
 		for (const genre of App.Porn.getGenresByType(type)) {