Don't crash when resource path is omitted

tests/ExifTest.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Resources.h"
 #include "SkCodec.h"
 #include "Test.h"
 
 static SkStreamAsset* resource(const char path[]) {
     SkString fullPath = GetResourcePath(path);
     return SkStream::NewFromFile(fullPath.c_str());
 }
 
 DEF_TEST(ExifOrientation, r) {
     SkAutoTDelete<SkStream> stream(resource("exif-orientation-2-ur.jpg"));
     REPORTER_ASSERT(r, nullptr != stream);
+    if (!stream) {
+        return;
+    }
+
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream.release()));
     REPORTER_ASSERT(r, nullptr != codec);
     SkCodec::Origin origin = codec->getOrigin();
     REPORTER_ASSERT(r, SkCodec::kTopRight_Origin == origin);
 
     stream.reset(resource("mandrill_512_q075.jpg"));
     codec.reset(SkCodec::NewFromStream(stream.release()));
     REPORTER_ASSERT(r, nullptr != codec);
     origin = codec->getOrigin();
     REPORTER_ASSERT(r, SkCodec::kTopLeft_Origin == origin);
 }