MagickCore/xwindow.c: remove not needed check (#1292)
MagickCore/xwindow.c: remove not needed check (#1292)

found by cppcheck

there's already check in line 3367
https://github.com/ImageMagick/ImageMagick/blob/master/MagickCore/xwindow.c#L3367
Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick