If $f(x) = \begin{cases} \sin x,x \ne n\pi ,n \in Z\\ \,\,\,\,\,\,0,\,\,{\rm{otherwise}} \end{cases}$ and $g(x) = \begin{cases} {x^2} + 1,x \ne 0,\,2\\ \,\,\,\,\,\,\,\,4,x = 0\\ \,\,\,\,\,\,\,\,\,5,x = 2 \end{cases}$ then $\underset{x\to 0}{\mathop{\lim }}\,g\{f(x)\}=$