WasmEmitter - Don't dereference a dyn_cast result. NFCI.

llvm-svn: 372165
diff --git a/llvm/lib/ObjectYAML/WasmEmitter.cpp b/llvm/lib/ObjectYAML/WasmEmitter.cpp
index e374764..42c57d4 100644
--- a/llvm/lib/ObjectYAML/WasmEmitter.cpp
+++ b/llvm/lib/ObjectYAML/WasmEmitter.cpp
@@ -518,7 +518,7 @@
     writeStringRef("reloc.DATA", OS);
     break;
   case wasm::WASM_SEC_CUSTOM: {
-    auto CustomSection = dyn_cast<WasmYAML::CustomSection>(&Sec);
+    auto *CustomSection = cast<WasmYAML::CustomSection>(&Sec);
     writeStringRef(("reloc." + CustomSection->Name).str(), OS);
     break;
   }