stackdriver: check if array is empty to prevent filter from crashing. This closes #13607

public/app/plugins/datasource/stackdriver/filter_segments.ts

@@ -87,7 +87,7 @@ export class FilterSegments {
     }
 
     // remove condition if it is first segment
-    if (index === 0 && this.filterSegments[0].type === 'condition') {
+    if (index === 0 && this.filterSegments.length > 0 && this.filterSegments[0].type === 'condition') {
       this.filterSegments.splice(0, 1);
     }
   }