Fix several wasm warnings an a use after free.

src/wasm/decoder.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_DECODER_H_
 #define V8_WASM_DECODER_H_
 
 #include "src/base/smart-pointers.h"
 #include "src/flags.h"
 #include "src/signature.h"
@@ skipping 180 matching lines @@
     Result<T> result;
     if (error_pc_) {
       result.error_code = kError;
       result.start = start_;
       result.error_pc = error_pc_;
       result.error_pt = error_pt_;
       result.error_msg = error_msg_;
       error_msg_.Reset(nullptr);
     } else {
       result.error_code = kSuccess;
-      result.val = val;
     }
+    result.val = val;
     return result;
   }
 
   // Resets the boundaries of this decoder.
   void Reset(const byte* start, const byte* end) {
     start_ = start;
     pc_ = start;
     limit_ = end;
     error_pc_ = nullptr;
     error_pt_ = nullptr;
@@ skipping 11 matching lines @@
   const byte* error_pt_;
   base::SmartArrayPointer<char> error_msg_;
 };
 
 #undef TRACE
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_DECODER_H_