show a clear error on nulls in inline strings in binary format (#1068)

* show a clear error on nulls in inline strings (which we don't support, and in general are not seen in practice, but are technically valid wasm) in binary format reading

Author: kripken

src/wasm/wasm-binary.cpp

@@ -1241,7 +1241,11 @@ Name WasmBinaryBuilder::getInlineString() {
   auto len = getU32LEB();
   std::string str;
   for (size_t i = 0; i < len; i++) {
-    str = str + char(getInt8());
+    auto curr = char(getInt8());
+    if (curr == 0) {
+      throw ParseException("inline string contains NULL (0). that is technically valid in wasm, but you shouldn't do it, and it's not supported in binaryen");
+    }
+    str = str + curr;
   }
   if (debug) std::cerr << "getInlineString: " << str << " ==>" << std::endl;
   return Name(str);