PVS-Studio warning V564 for DOSBox

static SDL_Surface * GFX_SetupSurfaceScaled(Bit32u sdl_flags,
                                            Bit32u bpp) {
  ...
  if (!sdl.blit.surface ||
     (!sdl.blit.surface->flags & SDL_HWSURFACE)) {
  ...
}

This is what should have been written here: !(sdl.blit.surface->flags & SDL_HWSURFACE)

This suspicious code was found in DOSBox project by PVS-Studio static code analyzer.
Warning message is:
V564 The '&' operator is applied to bool type value. You've probably forgotten to include parentheses or intended to use the '&&' operator. dosbox sdlmain.cpp 519

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/