[ignition] BytecodeGraphBuilder: Merge correct environment in try block

test/mjsunit/regress/regress-crbug-651403.js

 // Copyright 2016 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.
 
-function f(t) {
-  var f = t || this;
-  for (var i in t) {
-    for (var j in t) {
-      (j);
-      continue;
+// Flags: --ignition-staging --turbo --always-opt
+
+function f () {
+  var x = "";
+  function g() {
+    try {
+      eval('');
+      return x;
+    } catch(e) {
     }
   }
+  return g();
 }
+
 f();