With irreducible loops, we can have a null destination.

bug:26684047
Change-Id: I23d1c74caec4aaebc05362a588f6cfec2132bdc8
diff --git a/test/564-checker-irreducible-loop/info.txt b/test/564-checker-irreducible-loop/info.txt
new file mode 100644
index 0000000..1e0dd02
--- /dev/null
+++ b/test/564-checker-irreducible-loop/info.txt
@@ -0,0 +1,2 @@
+Regression test for optimizing in the presence of
+an irreducible loop.