Win32: Swap maskColor assignment based on alpha value

Looks like mask pixels was inverted.

(cherry picked from commit 362165ed9bca5e758e310f191129ce3600d13ed2)

src/core/windows/SDL_windows.c

@@ -600,7 +600,7 @@ HICON WIN_CreateIconFromSurface(SDL_Surface *surface)
         for (int x = 0; x < width; x++) {
             BYTE* pixel = (BYTE*)pBits + (y * width + x) * 4;
             BYTE alpha = pixel[3];
-            COLORREF maskColor = (alpha == 0) ? RGB(0, 0, 0) : RGB(255, 255, 255);
+            COLORREF maskColor = (alpha == 0) ? RGB(255, 255, 255) : RGB(0, 0, 0);
             SetPixel(hdcMem, x, y, maskColor);
         }
     }