Fix simple-magnification GM in "--preAbandonGpuContext" mode

Change-Id: Ia225464e9c58a0aeb2f63b7ca5d5025fc6891598
Reviewed-on: https://skia-review.googlesource.com/8260
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/gm/simple_magnification.cpp b/gm/simple_magnification.cpp
index a0d0395..402a7de 100644
--- a/gm/simple_magnification.cpp
+++ b/gm/simple_magnification.cpp
@@ -15,6 +15,9 @@
         SkImageInfo ii = SkImageInfo::Make(size, size, kN32_SkColorType, kPremul_SkAlphaType);
         sk_sp<SkSurface> surf(SkSurface::MakeRenderTarget(context, SkBudgeted::kYes, ii, 0,
                                                           origin, nullptr));
+        if (!surf) {
+            return nullptr;
+        }
 
         SkCanvas* canvas = surf->getCanvas();
 
@@ -91,6 +94,9 @@
 
         sk_sp<SkImage> bottomLImg = make_image(context, kImgSize, kBottomLeft_GrSurfaceOrigin);
         sk_sp<SkImage> topLImg = make_image(context, kImgSize, kTopLeft_GrSurfaceOrigin);
+        if (!bottomLImg || !topLImg) {
+            return;
+        }
 
         int bigOffset = 2 * kPad + kImgSize;