gegl-tool: blacklist lens-correct and hstack since they can't be used with the gegl tool.

lens-correct expect a lens correction model
hstack expect and aux buffer

app/tools/gimpgegltool.c

@@ -256,6 +256,8 @@ gimp_gegl_tool_operation_blacklisted (const gchar *name,
     "gegl:contrast-curve",
     "gegl:fill-path",
     "gegl:vector-stroke",
+    "gegl:lens-correct",
+    "gegl:hstack",
     "gimp-",
     "gimp:"
   };