Exactly as the pdepe documentation explains (and its examples show) you need to provide three function handles as its 2nd, 3rd, and 4th inputs. Instead your code calls those three functions without any input arguments, thus the error message.
You can define three function handle like this:
sol = pdepe(m, @pde1pde, @pde1ic, @pde1bc, x, t);
% ^ ^ ^ define function handles