Fix DART_CHECK_VALID macro.

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
diff --git a/runtime/include/dart_api.h b/runtime/include/dart_api.h
index 96ca0965652eebb7d1fc427f76328ce5c3fcea4b..56a2ae7e4951bf230a8ed3ec5e81d2c49c858550 100755
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -327,11 +327,14 @@ DART_EXPORT void _Dart_ReportErrorHandle(const char* file,
  *
  * Provided for convenience.
  */
-#define DART_CHECK_VALID(handle)                                        \
-  if (Dart_IsError((handle))) {                                         \
-    _Dart_ReportErrorHandle(__FILE__, __LINE__,                       \
-                              #handle, Dart_GetError(handle));          \
-  }
+#define DART_CHECK_VALID(handle)                                               \
+  {                                                                            \
+    Dart_Handle __handle = handle;                                             \
+    if (Dart_IsError((__handle))) {                                            \
+      _Dart_ReportErrorHandle(__FILE__, __LINE__,                              \
+                              #handle, Dart_GetError(__handle));               \
+    }                                                                          \
+  }                                                                            \
 
 
 /**