[turbofan] Fix an assertion in representation selection for BooleanNot.

test/mjsunit/compiler/regress-736567.js

+// Copyright 2017 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
+
+function f(b, x) {
+  var o = b ? { a : 1 } : undefined;
+  return o.a + !(x & 1);
+}
+
+f(1);
+
+function g() {
+  f(0, "s");
+}
+
+assertThrows(g);
+%OptimizeFunctionOnNextCall(g);
+assertThrows(g);