# Singular objects break after using in Sage

I don't understand why this code breaks:

```
R1 = singular.ring('(0,a)','(x,y)','dp')
f1 = singular('x^2')
g1 = singular('x')
fsage = f1.sage()
gsage = g1.sage()
print(f1)
print(g1)
print(fsage)
print(gsage)
g2 = fsage.reduce(gsage)
print(g2)
print(f1)
```

It gives this result:

```
x^2
x
x^2
x
0
Traceback (most recent call last): print(g1)
File "", line 1, in <module>
File "/tmp/tmpO7_2ph/___code___.py", line 13, in <module>
exec compile(u'print(f1)
File "", line 1, in <module>
File "/home/sage/sage-7.2/local/lib/python2.7/site-packages/sage/interfaces/singular.py", line 1318, in __repr__
elif self.type() == 'matrix':
File "/home/sage/sage-7.2/local/lib/python2.7/site-packages/sage/interfaces/singular.py", line 2059, in type
return m.group(1)
AttributeError: 'NoneType' object has no attribute 'group'
```

f1 prints fine the first time, but after running the reduce, it seems like it no longer exists. I'm trying to use f1 for other things after doing a reduce, but can't seem to find any way to do it.