PVS-Studio warning V595 for Wolf

FT_Error FT_Get_Glyph( FT_GlyphSlot slot,
  FT_Glyph *aglyph )
{
  FT_Library library = slot->library;
  FT_Error error;
  FT_Glyph glyph;

  const FT_Glyph_Class*  clazz = 0;

  if ( !slot ) {
    return FT_Err_Invalid_Slot_Handle;
  }
  ...
}

This suspicious code was found in Wolf project by PVS-Studio static code analyzer.
Warning message is:
V595 The 'slot' pointer was utilized before it was verified against nullptr. Check lines: 477, 484.   renderer  ftglyph.c  477

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/