SEGFAULT in matrix_mod_pn for padic extensions

Imported from <a href="http://trac.sagemath.org/sage_trac/ticket/13617">trac #13617</a>.



Reported by: saraedum

Component: padics

CC: 

Report Upstream: N/A

Authors: Julian Rueth

Dependencies: 

Work issues: 

Reviewers: David Roe, Punarbasu Purkayastha

Merged in: sage-5.9.beta1

Attachments: <ol><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13617/trac_13617.patch">trac_13617.patch: </a> by saraedum at 20121025T02:11:31</li><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13617/13617_review.patch">13617_review.patch: </a> by roed at 20130318T19:10:45</li></ol>