Don't crash when resource path is omitted

tests/ColorSpaceTest.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 "SkColorSpace.h"
 #include "Test.h"
 
 #include "png.h"
 
 static SkStreamAsset* resource(const char path[]) {
     SkString fullPath = GetResourcePath(path);
     return SkStream::NewFromFile(fullPath.c_str());
 }
 
 static bool almost_equal(float a, float b) {
     return SkTAbs(a - b) < 0.001f;
 }
 
 DEF_TEST(ColorSpaceParsePngICCProfile, r) {
     SkAutoTDelete<SkStream> stream(resource("color_wheel_with_profile.png"));
     REPORTER_ASSERT(r, nullptr != stream);
+    if (!stream) {
+        return;
+    }
 
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream.release()));
     REPORTER_ASSERT(r, nullptr != codec);
 
 #if (PNG_LIBPNG_VER_MAJOR > 1) || (PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR >= 6)
     SkColorSpace* colorSpace = codec->getColorSpace();
     REPORTER_ASSERT(r, nullptr != colorSpace);
 
     // No need to use almost equal here.  The color profile that we have extracted
     // actually has a table of gammas.  And our current implementation guesses 2.2f.
@@ skipping 47 matching lines @@
     REPORTER_ASSERT(r, almost_equal(0.385117f, xyz.fMat[0]));
     REPORTER_ASSERT(r, almost_equal(0.716904f, xyz.fMat[1]));
     REPORTER_ASSERT(r, almost_equal(0.0970612f, xyz.fMat[2]));
     REPORTER_ASSERT(r, almost_equal(0.143051f, xyz.fMat[3]));
     REPORTER_ASSERT(r, almost_equal(0.0606079f, xyz.fMat[4]));
     REPORTER_ASSERT(r, almost_equal(0.713913f, xyz.fMat[5]));
     REPORTER_ASSERT(r, almost_equal(0.436035f, xyz.fMat[6]));
     REPORTER_ASSERT(r, almost_equal(0.222488f, xyz.fMat[7]));
     REPORTER_ASSERT(r, almost_equal(0.013916f, xyz.fMat[8]));
 }