No longer accept NULL values in value_bits_valid and value_bits_synthetic_pointer

[Pedro Alves]

Following up on
<http://sourceware.org/ml/gdb-patches/2011-02/msg00201.html>.

I've checked in this patch.  We shouldn't be getting
NULL values here anymore.  If I missed a case were we do, the
offending caller needs to be fixed to not pass it.

Pedro Alves

2011-02-14  Pedro Alves  <pedro@codesourcery.com>

	* value.c (value_bits_valid, value_bits_synthetic_pointer):
	No longer handle NULL values.