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

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);
                 }