message: [Assembler] Add error message on empty symbols
diff: @@ -140,6 +140,9 @@ protected:
  if (symbols.count(cleanedSymbol) != 0) {
  return {Error(sourceLine, "Multiple definitions of symbol '" + cleanedSymbol + "'")};
  } else {
  + if (cleanedSymbol.isEmpty()) {
  + return {Error(sourceLine, "Invalid symbol")};
  + }
  symbols.insert(cleanedSymbol);
  }
  } else {
  