Fix missing lock release in exqlite_deserialize on malloc failure

When sqlite3_malloc fails, the function returned without calling
connection_release_lock, leaving the connection permanently locked.
Any subsequent call on that connection would deadlock indefinitely.

Author: mjc

c_src/sqlite3_nif.c

@@ -1055,6 +1055,7 @@ exqlite_deserialize(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
     size   = serialized.size;
     buffer = sqlite3_malloc(size);
     if (!buffer) {
+        connection_release_lock(conn);
         return make_error_tuple(env, am_deserialization_failed);
     }