Don't EnsureHasInitialMap on non-constructors

test/mjsunit/regress/regress-ensure-initial-map.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --allow-natives-syntax
 
-var a = [];
-for (var i = -20; i < 0; ++i) {
-  a[i] = 0;
+var x = Object.getOwnPropertyDescriptor({get x() {}}, "x").get;
+function f(o, b) {
+  if (b) {
+    return o instanceof x;
+  }
 }
 
+%OptimizeFunctionOnNextCall(f);
+f();
+
 function g() {
-    [].push.apply(a, arguments);
+  return new x();
 }
 
-function f() {
-  g();
-}
-
-g();
-g();
-%OptimizeFunctionOnNextCall(f);
-f();
+%OptimizeFunctionOnNextCall(g);
+assertThrows(()=>g());