Kotlin out of bounds exception

fun main() {
print(anagram("roma", "roma"))
}

fun strlenWithoutSpaces(string : String) : Int{
    var counter=0
    for(char in string){
        if (char==' ') continue
        counter++
    }
    return counter
}

fun anagram(string1: String, string2: String): Boolean{
    if (strlenWithoutSpaces(string1)!=strlenWithoutSpaces(string2)) return false
    var stringBuilder1= StringBuilder(string1)
    var stringBuilder2=StringBuilder(string2)

    for(index1 in stringBuilder1.indices){
        if (stringBuilder1.get(index1).equals(' ')) continue
        for (index2 in stringBuilder2.indices){
            if (stringBuilder1.get(index1).equals(stringBuilder2.get(index2))) stringBuilder2.deleteCharAt(index2)
            else if (stringBuilder2.get(index2).equals(' ')) stringBuilder2.deleteCharAt(index2)
        }
    }

    if(stringBuilder2.isEmpty()) return true   //string2 can be empty and not an anagram of string1 only if they differ in size, but I've checked for it at the beginning
    return false
}