Проверка на ошибку программы

[Razdolbai]

Unhandled Exception: System.IndexOutOfRangeException: Index was outside the boun
ds of the array.
at System.String.get_Chars(Int32 index)
at ardabyev_words_search_113b.ardabyev _words_search_113b.$Main() in F:\Pascal
ABC.NET\Projects\Kazbekov\words_sea rch\ardabyev_words_search_113b.pas: line 38
at ardabyev_words_search_113b.Program. Main()Программа завершена, нажмите любу
ю клавишу . . .

почему выдаёт такую ошибку?

program ardabyev_words_search_113b;
uses
  CRT;
var
  words: array of string;
  aString, temp, userValue, path: string;
  aText: Text;
  wordsCount: integer;
  i: longint;
  flag: char;
begin
  repeat
    flag := #0;
    ClrScr;
    writeln('Type a path to your .txt file (for ex.:, C:\books\text.txt):');
    readln(path);
    Assign(aText, path);
    Reset(aText);
    wordsCount := 0;
    while flag <> #13 do
    begin
      writeln('Enter a letter or word, the first letter of which to be carried out search:');
      readln(userValue);
      writeln('Press Enter to confirm a valid entrance or any another key to fix the entered values');
      flag := ReadKey;
    end;
    writeln();
    while not Eof(aText) do
    begin
      readln(aText, aString);
      for i := 1 to length(aString) do
        if (aString[i] <> ' ') and (i <> length(aString)) then
        begin
          if aString[i] in ['A'..'z', 'А'..'я'] then
            temp := temp + LowerCase(aString[i]);
        end
        else
          if temp[1] = LowerCase(userValue[1]) then
          begin
            if i = length(aString) then
              temp := temp + LowerCase(aString[i]);
            Inc(wordsCount);
            SetLength(words, wordsCount);
            words[wordsCount - 1] := temp;
            temp := '';
          end
          else
            temp := '';
    end;
    if wordsCount = 0 then
      writeln('There are no words that start with your letter in the text')
    else
      writeln('Found words for the letter ', userValue[1], ':');
    Close(aText);
    for i := 1 to wordsCount do
      writeln(i, ': ', words[i - 1]);
    words := nil;
    writeln('Press any key to restart or Esc to exit');
    flag := ReadKey;
  until flag = #27;
end.

вот код

[evg_m]

и temp и uservalue могут не иметь символов (='' \ length(..)=0 )
в этом случае uservalue[1] (temp[1]) и есть

Index was outside the boun
ds of the array.