Hey Matthew,
I managed to solve the problem.
Your suggestion was very good, but there is another method which needs to be corrected.
IF_RSPC_GET_VARIANT~EXISTS.
* CALL METHOD CL_RSPC_VARIANT=>EXISTS "Not necessary, as there is no variant
r_existys = rs_c_true.
With this little line of code, BW will not ask for a variant anymore. The chain runs without any problems.