Unfortunately glm does not support vectors with one entry or matrices with one row or column. glm_mat_1 changes that by implementing the missing functions and types for glm::mat<1,R,T,Q>, glm::mat<C,1,T,Q> and glm::mat<1,1,T,Q> for C, R in [2,3,4].
Requires glm version >= 0.9.9.1