src: fix use of uninitialized variable

Variable was uninitialized in 72547fe28d
Initialize the variable and add a static_check

PR-URL: https://github.com/nodejs/node/pull/9281
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/node_i18n.cc

@@ -586,7 +586,9 @@ static void GetStringWidth(const FunctionCallbackInfo<Value>& args) {
   TwoByteValue value(env->isolate(), args[0]);
   // reinterpret_cast is required by windows to compile
   UChar* str = reinterpret_cast<UChar*>(*value);
-  UChar32 c;
+  static_assert(sizeof(*str) == sizeof(**value),
+                "sizeof(*str) == sizeof(**value)");
+  UChar32 c = 0;
   UChar32 p;
   size_t n = 0;
   uint32_t width = 0;