Get rid of most instance of 'foo == NULL'

fpdfsdk/src/javascript/JS_Value.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "JS_Value.h"
 
 #include <time.h>
 #include <cmath>
@@ skipping 593 matching lines @@
   _get_timezone(&timezone);
 #endif
   return (double)(-(timezone * 1000));
 }
 
 int _getDaylightSavingTA(double d) {
   if (!FSDK_IsSandBoxPolicyEnabled(FPDF_POLICY_MACHINETIME_ACCESS))
     return 0;
   time_t t = (time_t)(d / 1000);
   struct tm* tmp = localtime(&t);
-  if (tmp == NULL)
+  if (!tmp)
     return 0;
   if (tmp->tm_isdst > 0)
     // One hour.
     return (int)60 * 60 * 1000;
   return 0;
 }
 
 double _Mod(double x, double y) {
   double r = fmod(x, y);
   if (r < 0)
@@ skipping 237 matching lines @@
   return day * 86400000 + time;
 }
 
 bool JS_PortIsNan(double d) {
   return d != d;
 }
 
 double JS_LocalTime(double d) {
   return JS_GetDateTime() + _getDaylightSavingTA(d);
 }