Don't crash when resource path is omitted

tests/ExifTest.cpp

Index: tests/ExifTest.cpp
diff --git a/tests/ExifTest.cpp b/tests/ExifTest.cpp
index c49de0f6fe2ed9b2244a472d48306bce0f798558..7fcd8b861d66820ef80fb8fcb905981db02a17ff 100644
--- a/tests/ExifTest.cpp
+++ b/tests/ExifTest.cpp
@@ -17,6 +17,10 @@ static SkStreamAsset* resource(const char path[]) {
 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();