Return pseudo-class image for -type bilevel option

MagickCore/quantize.c

diff --git a/MagickCore/quantize.c b/MagickCore/quantize.c
index 476d938..5c3a4be 100644
--- a/MagickCore/quantize.c
+++ b/MagickCore/quantize.c
@@ -496,12 +496,16 @@
 {
 #define AssignImageTag  "Assign/Image"
 
+  ColorspaceType
+    colorspace;
+
   ssize_t
     y;
 
   /*
     Allocate image colormap.
   */
+  colorspace=image->colorspace;
   if (cube_info->quantize_info->colorspace != UndefinedColorspace)
     (void) TransformImageColorspace(image,cube_info->quantize_info->colorspace,
       exception);
@@ -665,7 +669,7 @@
     }
   (void) SyncImage(image,exception);
   if (cube_info->quantize_info->colorspace != UndefinedColorspace)
-    (void) TransformImageColorspace(image,image->colorspace,exception);
+    (void) TransformImageColorspace(image,colorspace,exception);
   return(MagickTrue);
 }