Unexpected termination of bas64 encoding c++ program

I was working with program that deals on how to encode the data by using Base64 encoding. my program was working well if i'll be using std::string_view of base64 characters, that is:-
std::string_view textEnc{"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz/+"}; But if i'll be using std::string instead of std::string_view, the program stops unexpected. I dont understand the reason, why this happens. I use MinGW (GCC 9.2.0).

#include <vector>
#include <string_view>
#include <string>
#include <cstddef>
#include <algorithm>
#include <iostream>


class Base64Encoder {

public:
    std::string toBase64(std::vector<unsigned char> const & data);

private:
    const std::string_view textEnc{"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789/+"}; 
    const char  paddingSymbol{'='};
};


std::string Base64Encoder::toBase64(std::vector<unsigned char> const & data) {

    std::string result{};
    result.resize(data.size() / 3 * 4);
    auto resultItr = result.begin();
    size_t i{0};
    size_t j{0};

    while(j++ < data.size() / 3) {

        unsigned int value = (data[i] << 16) | (data[i + 1] << 8) | (data[i + 2]);
        i+=3;

        *resultItr++ = textEnc[(value & 0x00fc0000) >> 18];
        *resultItr++ = textEnc[(value & 0x003f0000) >> 12];
        *resultItr++ = textEnc[(value & 0x00000fc0) >> 6];
        *resultItr++ = textEnc[value & 0x0000003f];
    }

    if(auto rest = data.size() / 3 - i; rest == 1) {

        *resultItr++ = textEnc[(data[i] & 0x000000fc) >> 2];
        *resultItr++ = textEnc[(data[i] << 4) & 0x00000003];
        *resultItr++ = paddingSymbol;
        *resultItr++ = paddingSymbol;

    } else {

        unsigned int value = (data[i] << 8) | (data[i + 1]);

        *resultItr++ = textEnc[(value & 0x0000fc00) >> 10];
        *resultItr++ = textEnc[(value & 0x000003f0) >> 4];
        *resultItr++ = textEnc[(value & 0x0000000f) << 2];
        *resultItr++ = paddingSymbol;


    }

    return result;

}
/**Helper machineries
//For constructing a string from vector and vice versa.
**/
namespace converter {

std::string toString(std::vector<unsigned char> const & data) {

    std::string result{};
    std::copy(std::begin(data), std::end(data), std::back_inserter((result)));
    return result;
}

std::vector<unsigned char> toVector(std::string_view data) {

    std::vector<unsigned char> result{};
    std::copy(begin(data), end(data), std::back_inserter((result)));
    return result;
}

}//End of namespace converter.



int main() {

    Base64Encoder enc;

    auto text = "textToBeEncoded";

    std::cout << "before: " << text;
    auto textEncoded = enc.toBase64(converter::toVector(text));

    std::cout << "\nAfter: " << textEncoded;

}