Fix null check in Cache.

Change-Id: I0e5924889c82fe47ea8e7e318b9a7694dc6afa61
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/189421
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

https://dart.googlesource.com/sdk/+/2c63f59c9db0cc8d23be24b824d2577a164a8f0d
diff --git a/commits.json b/commits.json
index 30baa04..69df075 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "external/github.com/flutter/engine":"09b2468785a3e07132cac1fba99b1beafdf9dcec",
   "external/github.com/flutter/flutter":"a0ba6464089f906fefbf610732b2c9a7b66a1260",
-  "sdk":"08cb8bebe16b6b6f04eb99742ef8decef73a2f10"
+  "sdk":"2c63f59c9db0cc8d23be24b824d2577a164a8f0d"
 }
\ No newline at end of file