message: [Assembler] Fix invalid index in zero directive
diff: @@ -137,7 +137,7 @@ Directive zeroDirective() {
  return {Error(line.sourceLine, "Invalid number of arguments (expected 1)")};
  }
  bool ok;
  - int value = getImmediate(line.tokens[1], ok);
  + int value = getImmediate(line.tokens.at(0), ok);
  if (!ok) {
  return {Error(line.sourceLine, "Invalid argument")};
  }
  