Sandro N. answered 02/13/20
Italian Language and Culture teacher in several American institutions
In older Italian “v’ha” can mean “c’è” (there is). The complete translation of the libretto’s excerpt:
Non disperate, o figli,
Non son perduti ancor:
V’ha un Nume protettor
Della sventura.
is
Do not despair, folks [even if literally: sons],
They are not dead [literally: lost] yet:
[Because] There’s a God who protects
From misfortune.