Corrigendum and addendum to “Moduli spaces of framed sheaves and quiver varieties”

This paper is an erratum to our paper Moduli spaces of framed sheaves and quiver varieties (J. Geom. Phys., 2016). As a byproduct, we prove a result (Prop. 2.5) providing a description of the fibre TV∨Gr(a,r)⊕n−1, for each V∈Gr(a,r), as the space of isomorphism classes of certain extensions of sheaves on Hirzebruch surfaces.