Fix an assert in lse.

Wrong assert. Just deleted it.

Change-Id: I6f051609d87b2c6da081ee63f783ce99462f8a09
diff --git a/compiler/optimizing/load_store_elimination.cc b/compiler/optimizing/load_store_elimination.cc
index 068d5db..5b89cfe 100644
--- a/compiler/optimizing/load_store_elimination.cc
+++ b/compiler/optimizing/load_store_elimination.cc
@@ -738,8 +738,6 @@
     }
     if (same_value || possibly_redundant) {
       possibly_removed_stores_.push_back(instruction);
-      // Same-value/singleton-field store shouldn't have a null check.
-      DCHECK(!ref->InputAt(0)->IsNullCheck());
     }
 
     if (!same_value) {