Since Mahayana Agama contains parallels in the Pali Cannon I am answering using the Suttas in the Pali Canon which I am more familiar with.
Abiding or contemplating the 3 characteristics [impermanence (anicca),
suffering (dukkha) and not-self (anatta)] is called abiding in emptiness. [Cula Sunnata Sutta, Maha Sunnata Sutta] The opposite of the 3 characteristics is perversions (vipallasa) [what is impermanent is taken to be permanent; what is painful is taken to be pleasurable; what is not self is taken to be a (or the) self; and what is impure is taken to be pure]. [Vipallasa Sutta] Hence non empty might mean something is deluded, i.e., conceptual constructions are empty since they breakdown under further scrutiny. Attachment to concepts, review and throughts or being subjected to the perversion is non empty.
They take untruth for truth; they take truth for untruth; such persons can never arrive at the truth, for they hold wrong views.
They take truth for truth; they take untruth for untruth; such persons arrive at the truth, for they hold right views. At the end of the discourse, many people came to be established in Sotapatti Fruition.
Source: Dhammapada Verses 11 and 12 Sariputtatthera Vatthu
Contrary to the usage on perversion described above someone taking untrue and truth, wrong view as right view, something of low value as valuable can be considered empty in this context and some one taking truth as the truth, ... can be considered non empty in this context.