reduce (finite field, mixed ordering) crashes

[ren]

trying to run the following lines of code

ring r = 2,(t,x(1..4)),ws(1,-1,-11,-3,-19);
ideal inI = t*x(3)*x(4)-t*x(1)*x(2),
-x(2)*x(3)*x(4)+t^2*x(1)*x(2)*x(3),
-x(2)*x(3)*x(4)^2+t^2*x(1)^2*x(2)^2;
ideal J = t*x(3)*x(4)-t*x(1)*x(2)+x(1)^2,
-x(2)*x(3)*x(4)+t^2*x(1)*x(2)*x(3)-t*x(1)^2*x(3),
-x(2)*x(3)*x(4)^2-t*x(1)^2*x(3)*x(4)+t^2*x(1)^2*x(2)^2-t*x(1)^3*x(2);
reduce(inI,std(J));

yields

                     SINGULAR                                 /  Development
 A Computer Algebra System for Polynomial Computations       /   version 4.0.1
                                                           0<
 by: W. Decker, G.-M. Greuel, G. Pfister, H. Schoenemann     \   Sep 2014
FB Mathematik der Universitaet, D-67653 Kaiserslautern        \
// ** executing /home/ren/Sources2/Singular/LIB/.singularrc
> ring r = 2,(t,x(1..4)),ws(1,-1,-11,-3,-19);
> ideal inI = t*x(3)*x(4)-t*x(1)*x(2),
. -x(2)*x(3)*x(4)+t^2*x(1)*x(2)*x(3),
. -x(2)*x(3)*x(4)^2+t^2*x(1)^2*x(2)^2;
> ideal J = t*x(3)*x(4)-t*x(1)*x(2)+x(1)^2,
. -x(2)*x(3)*x(4)+t^2*x(1)*x(2)*x(3)-t*x(1)^2*x(3),
. -x(2)*x(3)*x(4)^2-t*x(1)^2*x(3)*x(4)+t^2*x(1)^2*x(2)^2-t*x(1)^3*x(2);
> reduce(inI,std(J));

// ***dError: assume violation at kutil.cc:7163 condition: p.pLength == 0 || pLength(p.p) == p.pLength || rIsSyzIndexRing(currRing)
Breakpoint 1, dErrorBreak () at dError.cc:142
142	{}

Note that this does NOT happen in older versions of Singular (e.g. the version installed on murrumesh).

[hannes]

cosmetic changes for assume: 100bd496fb3125687ec86ff10fc3604c78620e47 crash is not reproducable