fix(server): 空のアンテナが作成できるのを修正

packages/backend/src/server/api/endpoints/antennas/create.ts

@@ -79,7 +79,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 		private globalEventService: GlobalEventService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
-			if (ps.keywords.length === 0) {
+			if ((ps.keywords.length === 0) || (ps.keywords[0].filter(x => x !== '').length === 0)) {
 				throw new Error('invalid param');
 			}