Remove handle from MD context in single hash config
diff --git a/library/md.c b/library/md.c
index abc2ad3..cbe92dd 100644
--- a/library/md.c
+++ b/library/md.c
@@ -1167,7 +1167,9 @@
         }
     }
 
+#if !defined(MBEDTLS_MD_SINGLE_HASH)
     ctx->md_info = md_info;
+#endif
 
     return( 0 );
 }