set degree() bug

[RobinHankin]

commit 65c1891 added some degree() functionality. But:

a <- rfalg(20)
 a
free algebra element algebraically equal to
+ 29*a + 12*aa + 16*abca + 37*b + 4*bacb + 5*bb + 17*bbb + 3*bc + 43*c + 2*cb +
19*cbac + 9*cbbc + 13*cca + 1*ccac
 degrees(a)
A disord object with hash 16b7a5e2f2bd4408b521e08e24d06823e8f4f78f and elements
 [1] 1 2 4 1 4 2 3 2 1 2 4 4 3 4
(in some order)
degree(a,1)
free algebra element algebraically equal to
+ 29*a + 37*b + 43*c
 degree(a,1) <- degree(a,1) * 5
Error in .local(x, i, j = j, ..., value) : 
  consistent(x[i], value) is not TRUE

The last line is perfectly well-defined and should work.

[RobinHankin]

Following the fixing of issue #21 this issue should be about grade(), not degree()