Before revision:  that may depend on a possibly infinite-dimensional parameter \beta\in   , we obtain a uniform bound on its operator norm of the form  \sup \sup} _{\beta \in   } ||X(\beta)|| \leq CK \left(\max(N,T)
After revision:  that may depend on a possibly infinite-dimensional parameter \beta\in  , we obtain a uniform bound on its operator norm of the form  \mathbb{E \sup} _{\beta \in  } ||X(\beta)|| \leq CK \left(\max(N,T)