Updates ckandumper: a88469c Check if file exists before attempt to get sha256sum

diff --git a/ckandumper b/ckandumper
index 060975ed25259cf19d3a7f4ef288fc35c64148ed..a88469c6d770e61577ee7408778baef20bddf31b 160000 (submodule)
--- a/ckandumper
+++ b/ckandumper
@@ -1 +1 @@
-Subproject commit 060975ed25259cf19d3a7f4ef288fc35c64148ed
+Subproject commit a88469c6d770e61577ee7408778baef20bddf31b