fixed NPE in case of incorrect partitioning name parameter (now you will see the normal log message with error)

(cherry picked from commit f247e96d97dfa136c553f9b359a47f33b2d60acf)

dao/src/main/java/org/thingsboard/server/dao/timeseries/NoSqlTsPartitionDate.java

@@ -66,6 +66,6 @@ public enum NoSqlTsPartitionDate {
                 }
             }
         }
-        return Optional.of(partition);
+        return Optional.ofNullable(partition);
     }
 }