[wasm] Handle no initial memory case correctly when memory is exported

test/mjsunit/regress/wasm/regression-699485.js

-// Copyright 2016 the V8 project authors. All rights reserved.
+// 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: --expose-wasm
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 (function() {
 "use asm";
 var builder = new WasmModuleBuilder();
 builder.addMemory(0, 5, false);
 builder.addFunction("regression_699485", kSig_i_v)
   .addBody([
       kExprI32Const, 0x04,
       kExprNop,
       kExprGrowMemory, 0x00,
       ]).exportFunc();
 let module = builder.instantiate();
 assertEquals(0, module.exports.regression_699485());
 })();