Loki: Fix throwing error when no labels received (#81077)

* Loki: Fix throwing error when no labels received

* Remove es code

public/app/plugins/datasource/loki/LanguageProvider.test.ts

@@ -138,6 +138,17 @@ describe('Language completion provider', () => {
         start: 1546372800000,
       });
     });
+
+    it('should work if request returns undefined', async () => {
+      const datasource = setup({});
+      datasource.getTimeRangeParams = jest
+        .fn()
+        .mockImplementation((range: TimeRange) => ({ start: range.from.valueOf(), end: range.to.valueOf() }));
+      const languageProvider = new LanguageProvider(datasource);
+      languageProvider.request = jest.fn().mockResolvedValue(undefined);
+      const series = await languageProvider.fetchSeriesLabels('stream', { timeRange: mockTimeRange });
+      expect(series).toEqual({});
+    });
   });
 
   describe('label values', () => {

public/app/plugins/datasource/loki/LanguageProvider.ts

@@ -172,6 +172,9 @@ export default class LokiLanguageProvider extends LanguageProvider {
     if (!value) {
       const params = { 'match[]': interpolatedMatch, start, end };
       const data = await this.request(url, params);
+      if (!Array.isArray(data)) {
+        return {};
+      }
       const { values } = processLabels(data);
       value = values;
       this.seriesCache.set(cacheKey, value);