[RoboN1X]

You're trying to check an empty string, you need to check it after sscanf is passed the string to shout variable.

pawn Код:

CMD:s(playerid, params[]) return cmd_shout(playerid, params);
CMD:shout(playerid, params[])
{
    new
        string[128],
        shout[100];
    if(sscanf(params, "s[100]", shout))
    {
        SendClientMessage(playerid, -1, ""COL_CYAN"[KORISTI]: "COL_WHITE"/(s)hout [text]");
        return 1;
    }
    else
    {
        if( IsCaps( shout ) )
        {
            SendClientMessage( playerid, -1, ""COL_RED"[GRESKA]: "COL_WHITE"Ne mozete pisati Caps Lockom, velika slova oznacavaju sukob! "COL_RED"Iskljucite"COL_WHITE" Caps Lock"COL_RED"!" );
            return 0;
        }
        format(string, sizeof(string), "%s se dere: %s!!",GetName(playerid),shout);
        ProxDetector(50.0, playerid, string, -1);
    }
    return 1;
}

Also what is text[i+6]? This is unnecessary, and wouldn't work, because it will do this:
"Just A Text" = 11chars + 1 \0
'A' <= text[6+6] <= 'Z' will return false, as it's \0
'A' <= text[7+6] <= 'Z' will return false, as there is no char at string 13.... (might probably stop working)
Also strlen will not count the \0 at the end, so you don't need to -1, unless you want also call "HAHAHa" as Caps.
So change to this, don't worry, all characters will be checked if it's capitals

pawn Код:

stock IsCaps( text[ ] ) 
{
    for( new i, j = strlen( text ); i < j; i ++ )
    {
        if( ( 'A' <= text[ i ] <= 'Z' ) )
            return true;
    }
    return false;
}

I didn't test it, but i hope it works (it should).