improve assertion


git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2087 35c25a1d-7b9e-4130-9fde-d3aeb78583b8
diff --git a/src/nano.c b/src/nano.c
index 845e602..b454c3f 100644
--- a/src/nano.c
+++ b/src/nano.c
@@ -672,7 +672,7 @@
 void unpartition_filestruct(partition *p)
 {
     char *tmp;
-    assert(p != NULL);
+    assert(p != NULL && fileage != NULL && filebot != NULL);
 
     /* Reattach the line above the top of the partition, and restore the
      * text before top_x from top_data.  Free top_data when we're done