Fix vulkan build on linux and android

src/gpu/vk/GrVkPipelineStateCache.cpp

Index: src/gpu/vk/GrVkPipelineStateCache.cpp
diff --git a/src/gpu/vk/GrVkPipelineStateCache.cpp b/src/gpu/vk/GrVkPipelineStateCache.cpp
index a250dcac995e4f3826afd6d1b6a82c540a4df9b8..fc3464c390302644b0b38789ed4b930ee40f6d66 100644
--- a/src/gpu/vk/GrVkPipelineStateCache.cpp
+++ b/src/gpu/vk/GrVkPipelineStateCache.cpp
@@ -104,7 +104,7 @@ sk_sp<GrVkPipelineState> GrVkResourceProvider::PipelineStateCache::refPipelineSt
                                        pipeline,
                                        *fGpu->vkCaps().glslCaps())) {
         GrCapsDebugf(fGpu->caps(), "Failed to build vk program descriptor!\n");
-        return false;
+        return nullptr;
     }
 
     // Get vulkan specific descriptor key