Looks like a bad copy / paste. The problem is in the definition of ω

ω // InputForm

(Tooltip[a*(1 - a^2*B^4*M^2), TraditionalForm] - (a^2 - 2*M*r + r^2)*
   Tooltip[(a*(r^2 + a^2*Cos[\[Theta]]^2))/((a^2 + r^2)^2 - a^2*(a^2 - 2*M*r + r^2)*Sin[\[Theta]]^2) + 
     (B^4*(-8*a*M*r*Cos[\[Theta]]^2*(3 - Cos[\[Theta]]^2) - 6*a*M*r*Sin[\[Theta]]^4 + (2*a^3*M*(2*a^2*M + a^2*r + r^3)*Sin[\[Theta]]^6)/
         ((a^2 + r^2)^2 - a^2*(a^2 - 2*M*r + r^2)*Sin[\[Theta]]^2) + (4*a^3*M^2*Cos[\[Theta]]^2*((a^2 + r^2)*(3 - Cos[\[Theta]]^2)^2 - 4*a^2*Sin[\[Theta]]^2))/
         ((a^2 + r^2)^2 - a^2*(a^2 - 2*M*r + r^2)*Sin[\[Theta]]^2)))/16, TraditionalForm])/(a^2 + r^2)