Here is another approach to the problem:
We know that,
REC(or decidable) ⊂ REL(or undecidable or semi undecidable) ⊂ U(totally undecidable). Where U denotes the set of all languages possible.
M halts on all inputs and hence surely that it will halt. Hence, decidable.
L(M) = L' such that L is undecidable. Taking complement and considering the set theory L' is decidable.
Intersection of it will give decidable language. Hence it is recursive.
Some answers states it to be regular. But I think, its recursive but we can’t be sure that it will be regular