NativeCrypto: not finding a key is not fatal

If we don't find a key in the keystore, we should just return null
reference. The only time we should throw exceptions is when the key
decoding failed or something else like that.

Bug: 20488918

(cherry picked from commit 8098cbbc7fbf2d22402da487465a153734f9f9b6)

Change-Id: I621b39257bc98d888f7ad390fb8648326c67dfc4
1 file changed