get_index_string_dim: Fix dimansion report for file = NULL
get_index_string_dim: Fix dimansion report for file = NULL

BlackLight/feh,Caellian/feh,yusiwen/feh,Caellian/feh,yusiwen/feh,Caellian/feh,BlackLight/feh,yusiwen/feh,BlackLight/feh,Caellian/feh