fix: closes #11511, reset skin if it was removed from bootswatch

src/upgrades/3.0.0/reset_bootswatch_skin.js

@@ -0,0 +1,17 @@
+'use strict';
+
+
+const db = require('../../database');
+
+module.exports = {
+	name: 'Reset bootswatch skin',
+	timestamp: Date.UTC(2023, 3, 24),
+	method: async function () {
+		const config = await db.getObject('config');
+		const currentSkin = config.bootswatchSkin || '';
+		const css = require('../../meta/css');
+		if (currentSkin && !css.supportedSkins.includes(currentSkin)) {
+			await db.setObjectField('config', 'bootswatchSkin', '');
+		}
+	},
+};