So when you say, “I saw you working,” you get a grammatical sentence with a verb (saw), followed by its object (you), followed by a modifier of that object (working).

Yet it’s clearly correct because the structure, with “Jen” as a noun and “walking” as a modifier of the noun, is both grammatical and standard.

Reading your writing in a new form — for example, on paper instead of on a screen; in a different font; or out loud — can be helpful in finding typos or grammatical errors.

Terence Parsons, Some Problems concerning the Logic of Grammatical Modifiers, Synthese, Vol. 21, No. 3/4, Semantics of Natural Language, I (Oct., 1970), pp. 320-334 ...

Broad match modifiers help advertisers control the intent of users seeing ads, but Bing says advertisers may have been missing out because of grammatical errors in queries.