fix BigInt gdb pretty-printer

since

commit 9536098ff1
Date:   Tue Nov 17 10:15:11 2020 +0200

    simplify BigInt, remove isSet

and

commit 33b8f7c10b
Date:   Wed Jan 6 10:41:22 2021 +0200

    bIsBig member is redundant

Change-Id: I877364d4b5ed11812c34f2b5d51ec60dd6cca9de
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/144215
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>

solenv/gdb/libreoffice/tl.py

@@ -18,13 +18,10 @@ class BigIntPrinter(object):
         self.val = val
 
     def to_string(self):
-        if self.val['bIsSet']:
-            if self.val['bIsBig']:
-                return self._value()
-            else:
-                return self.val['nVal']
+        if self.val['nLen']:
+            return self._value()
         else:
-            return "unset %s" % self.typename
+            return self.val['nVal']
 
     def _value(self):
         len = self.val['nLen']