Removed incorrect assert in equation_systems.C. Assert is no longer valid now that we can plot a subset of the systems in an EquationSystems object.
Removed incorrect assert in equation_systems.C. Assert is no longer valid now that we can plot a subset of the systems in an EquationSystems object.

Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh