Remove unnecessary NULL checks, part 4.

Finish up crypto, minus the legacy modules we haven't been touching much.

Change-Id: I0e9e1999a627aed5fb14841f8a2a7d0b68398e85
Reviewed-on: https://boringssl-review.googlesource.com/4517
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/stack/stack.c b/crypto/stack/stack.c
index bc8c6f8..c584515 100644
--- a/crypto/stack/stack.c
+++ b/crypto/stack/stack.c
@@ -86,9 +86,7 @@
   return ret;
 
 err:
-  if (ret) {
-    OPENSSL_free(ret);
-  }
+  OPENSSL_free(ret);
   return NULL;
 }
 
@@ -324,9 +322,7 @@
   return ret;
 
 err:
-  if (ret) {
-    sk_free(ret);
-  }
+  sk_free(ret);
   return NULL;
 }