Handle promise texture image fulfill returning nullptr.

Bug: chromium:948249
Change-Id: Id5d9b732a0d9612b7ed562041fa3544fd7c39f71
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/206076
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/GrFragmentProcessor.h b/src/gpu/GrFragmentProcessor.h
index fecf8d5..5136243 100644
--- a/src/gpu/GrFragmentProcessor.h
+++ b/src/gpu/GrFragmentProcessor.h
@@ -434,8 +434,7 @@
     // TODO: this can go away once explicit allocation has stuck
     bool instantiate(GrResourceProvider* resourceProvider) const {
         if (resourceProvider->explicitlyAllocateGPUResources()) {
-            SkASSERT(fProxyRef.get()->isInstantiated());
-            return true;
+            return fProxyRef.get()->isInstantiated();
         } else {
             return SkToBool(fProxyRef.get()->instantiate(resourceProvider));
         }