fix: Make getTopScoringIntent return '' instead of undefined

libraries/botbuilder-core/src/recognizerResult.ts

@@ -46,7 +46,7 @@ export const getTopScoringIntent = (result: RecognizerResult): { intent: string;
         throw new Error('result is empty');
     }
 
-    let topIntent: string;
+    let topIntent: string = '';
     let topScore = -1;
     for (const [intentName, intent] of Object.entries(result.intents)) {
         const score = intent.score ?? -1;

libraries/botbuilder-core/tests/getTopScoringIntent.test.js

@@ -0,0 +1,16 @@
+const assert = require('assert');
+const { getTopScoringIntent} = require('../lib');
+
+describe('getTopScoringIntent', function () {
+    it(' should never return undefined', function () {
+        let result = getTopScoringIntent({
+            text: '',
+            intents: {},
+            entities: {}
+        });
+
+        assert.notStrictEqual(result.intent, undefined);
+        assert.strictEqual(result.intent, '');
+    });
+
+});

libraries/botbuilder-dialogs-adaptive/src/recognizers/crossTrainedRecognizerSet.ts

@@ -186,7 +186,7 @@ export class CrossTrainedRecognizerSet extends AdaptiveRecognizer implements Cro
      * @returns {boolean} Boolean result of whether or not an intent begins with the `DeferToRecognizer_` prefix.
      */
     private isRedirect(intent: string): boolean {
-        return intent.startsWith(deferPrefix);
+        return intent?.startsWith(deferPrefix) ?? false;
     }
 
     /**