Singular/Sources — pull request #514 by jakobkroeker (2014-02-17 18:02:55+00:00)
Title: fix for bug 527 and correct return data structure in case zero ideal is passed to primdecZ

fixes also the following sort of bugs:
1.
in the past `primdecZ(ideal(0))`
returned
```
list(ideal(0),ideal(0))
[1]
_[1]=0
[2]
_[1]=0

```
but correct is:
```
list(list(ideal(0),ideal(0)))
[1]
[1]
_[1]=0
[2]
_[1]=0

```

2.
```
ring rng = integer, (xk,xx),dp;
ideal I = 8*xk;
primdecZ(I);
? identifier C not found in Shelp
? error occurred in or before primdecint.lib::extractZ line 1123: ` list C=imap(Shelp,C);`
? leaving primdecint.lib::extractZ
```