Fix ParseISOTime to handle short HH:MM format without seconds

[bero]

Summary

ParseISOTime accepted the HH:MM format pattern but crashed when parsing because it always tried to read seconds from position 7.

Bug Description

The function pattern matching allowed ##:## format:

if not MatchPattern('##:##:##:###', str)
  and not MatchPattern('##:##:##.###', str)
  and not MatchPattern('##:##:##', str)
  and not MatchPattern('##:##', str) then  // <-- Accepts HH:MM
    raise EBold.CreateFmt(sInvalidTimeFormat, [str]);
But then unconditionally tried to parse seconds:
s := StrToInt(copy(str, 7, 2));  // <-- Crashes on '14:30' with '' is not a valid integer

Steps to Reproduce

var dt: TDateTime;
begin
  dt := ParseISOTime('14:30');  // Raises EConvertError: '' is not a valid integer value
end;

Fix

Check string length before parsing seconds:

if Length(str) >= 8 then
begin
  s := StrToInt(copy(str, 7, 2));
  if s > 59 then
    raise EBold.CreateFmt(sInvalidTimeFormatLargeSecond, [str]);
end
else
  s := 0;

UnitTest added to testproject