have some errors that keep re appearing.

I am looking through a massive debug log and have some errors that keep re appearing.
Can anyone tell me what this is?

[20-Apr-2017 21:13:39 UTC] PHP Notice: is_singular was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. Please see Debugging in WordPress for more information. (This message was added in version 3.1.0.) in /home/lucidhive/public_html/lucidhive/wp-includes/functions.php on line 4137