Merge pull request #14900 from Microsoft/Fix14892

Fix #14892: Add undefined check before using the intializer of for-statment

src/compiler/transformers/generators.ts

@@ -1478,7 +1478,7 @@ namespace ts {
             }
 
             const initializer = node.initializer;
-            if (isVariableDeclarationList(initializer)) {
+            if (initializer && isVariableDeclarationList(initializer)) {
                 for (const variable of initializer.declarations) {
                     hoistVariableDeclaration(<Identifier>variable.name);
                 }

src/compiler/transformers/module/system.ts

@@ -1287,6 +1287,10 @@ namespace ts {
          * @param node The node to visit.
          */
         function visitForInitializer(node: ForInitializer): ForInitializer {
+            if (!node) {
+                return node;
+            }
+
             if (shouldHoistForInitializer(node)) {
                 let expressions: Expression[];
                 for (const variable of node.declarations) {