bugfix for adjoints with user-provided initial sensitivities
bugfix for adjoints with user-provided initial sensitivities

FFroehlich/AMICI,AMICI-developer/AMICI,FFroehlich/AMICI,FFroehlich/AMICI,AMICI-developer/AMICI,AMICI-developer/AMICI,AMICI-developer/AMICI,FFroehlich/AMICI