No label defined (Q1163)

\Phi(q) = \begin{cases}0 & \quad q = 0 \\1 & \quad q = 1 \\-1 & \quad q = -1 \\2^m (2n + 1) & \quad q =\frac{m}{n} \text{ simplest form } \\- 2^m(2n + 1) & \quad q = - \frac{m}{n} \text{ simplest form}\end{cases}