Why is there an extra letter appearing with screen buffers - c++

Question

So I tried making a basic game for testing movement with console. I decided to use screen buffers, but when I compile and run the c++ code the letter a appears with the player (character #)
Here's the code:
#include "pch.h"
#include <iostream>
#include <stdio.h>
#include <Windows.h>
int width = 50, height = 20;
int main()
{
wchar_t *screen = new wchar_t[width * height];
HANDLE hConsole = CreateConsoleScreenBuffer(GENERIC_READ | GENERIC_WRITE, 0, NULL, CONSOLE_TEXTMODE_BUFFER, NULL);
SetConsoleActiveScreenBuffer(hConsole);
DWORD bytesWritten = 0;
int x = width / 2, y = height / 2;
while (true) {
screen[width * height - 1] = '\0';
for (int i = 0; i < width * height; i++) screen[i] = L' ';
if (GetAsyncKeyState('W') & 1) y--;
else if (GetAsyncKeyState('S') & 1) y++;
if (GetAsyncKeyState('A') & 1) x--;
else if (GetAsyncKeyState('D') & 1) x++;
// keep the character inside
if (x < 0) x = 0;
else if (x > width-1) x = width-1;
if (y < 0) y = 0;
else if (y > height - 1) y = height - 1;
wsprintf(&screen[width * y + x], L"#");
WriteConsoleOutputCharacter(hConsole, screen, width * height, { 0,0 }, &bytesWritten);
}
return 0;
}
Running it looks like this:
I use visual studio 2017.
Why does the letter a appear?
Thanks in advance!