Don't crash when return type jsdoc tag is malformed

Fixes #6662

Author: RyanCavanaugh

src/compiler/checker.ts

@@ -10344,7 +10344,7 @@ namespace ts {
 
         function getReturnTypeFromJSDocComment(func: SignatureDeclaration | FunctionDeclaration): Type {
             const returnTag = getJSDocReturnTag(func);
-            if (returnTag) {
+            if (returnTag && returnTag.typeExpression) {
                 return getTypeFromTypeNode(returnTag.typeExpression.type);
             }
         }

tests/cases/fourslash/getJavaScriptQuickInfo7.ts

@@ -0,0 +1,19 @@
+/// <reference path="fourslash.ts" />
+
+// @allowNonTsExtensions: true
+// @Filename: file.js
+//// /**
+////  * This is a very cool function that is very nice.
+////  * @returns something
+////  */
+//// function a1() {
+//// 	try {
+//// 		throw new Error('x');
+//// 	} catch (x) { x--; }
+//// 	return 23;
+//// }
+//// 
+//// x - /**/a1()
+
+goTo.marker();
+verify.quickInfoExists();