Minecraft Forge (and many mods) have problems with the Turkish locale because they expect that for the basic ASCII letters A-Z the uppercase and lowercase conversions result in the same ASCII-result, e.g. i<->I. However for the Turkish locale that isn't true. There i<->İ and ı<->I.
This small mod does one thing when the game starts: If it detects a Turkish locale, it changes it to English.
This can fix many issues surrounding mods that use toLowerCase and toUpperCase without specifying a locale, especially when one's computer is set to the Turkish locale. Installing this mod will not change gameplay or language settings at all, it only exists to fix a few specific crashes.