Fix #19137: handle when regexp doesn't match in constructorNameFallback

sdk/lib/_internal/js_runtime/lib/js_helper.dart

Index: sdk/lib/_internal/js_runtime/lib/js_helper.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/js_helper.dart b/sdk/lib/_internal/js_runtime/lib/js_helper.dart
index ab3f79c999471470f3a972deb09b10cda8f3d79b..d6dd538c03993dd5d2a5ab8a739371179bf222af 100644
--- a/sdk/lib/_internal/js_runtime/lib/js_helper.dart
+++ b/sdk/lib/_internal/js_runtime/lib/js_helper.dart
@@ -891,9 +891,9 @@ class Primitives {
         // an identifier, we use that instead of the very generic 'Object'.
         var objectConstructor = JS('', '#.constructor', object);
         if (JS('bool', 'typeof # == "function"', objectConstructor)) {
-          var decompiledName =
-              JS('var', r'#.match(/^\s*function\s*([\w$]*)\s*\(/)[1]',
-                  JS('var', r'String(#)', objectConstructor));
+          var match = JS('var', r'#.match(/^\s*function\s*([\w$]*)\s*\(/)',
+              JS('var', r'String(#)', objectConstructor));
+          var decompiledName = match == null ? null : JS('var', r'#[1]', match);
           if (decompiledName is String &&
               JS('bool', r'/^\w+$/.test(#)', decompiledName)) {
             name = decompiledName;