Convex Hull kernel fix

diff --git a/magick/morphology.c b/magick/morphology.c
index faeb115..cdd8627 100644
--- a/magick/morphology.c
+++ b/magick/morphology.c
@@ -1819,13 +1819,13 @@
         if (kernel == (KernelInfo *) NULL)
           return(kernel);
         kernel->type = type;
-        ExpandRotateKernelInfo(kernel, 45.0);
+        ExpandRotateKernelInfo(kernel, 90.0);
         /* append the mirror versions too - no flip function yet */
         new_kernel=ParseKernelArray("3: 1,1,1  1,0,-  -,-,0");
         if (new_kernel == (KernelInfo *) NULL)
           return(DestroyKernelInfo(kernel));
         new_kernel->type = type;
-        ExpandRotateKernelInfo(new_kernel, 45.0);
+        ExpandRotateKernelInfo(new_kernel, 90.0);
         LastKernelInfo(kernel)->next = new_kernel;
         break;
       }