Make SkBlend_optsTests fail rather than crash when resources are missing

BUG=skia:5314

TBR=herb@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1987143002

Review-Url: https://codereview.chromium.org/1987143002
diff --git a/tests/SkBlend_optsTest.cpp b/tests/SkBlend_optsTest.cpp
index ee60d5e..06b7c1a 100644
--- a/tests/SkBlend_optsTest.cpp
+++ b/tests/SkBlend_optsTest.cpp
@@ -62,13 +62,14 @@
 
     std::string fileName = resourceName + ".png";
     sk_sp<SkImage> image = GetResourceAsImage(fileName.c_str());
-    SkASSERT(image != nullptr);
     if (image == nullptr) {
-        SkFAIL("image is NULL");
+        ERRORF(reporter, "image is NULL");
+        return;
     }
     SkBitmap bm;
     if (!as_IB(image)->getROPixels(&bm)) {
-        SkFAIL("Could not read resource");
+        ERRORF(reporter, "Could not read resource");
+        return;
     }
 
     SkPixmap pixmap;