Fixed bug in debugging information in dex file

Rationale:
Not resetting signature field may cause "leaking" old extended
value into new non-extended value (exposed while implementing
an Art-based dexdump; it affects all debug iterators though)

Bug: 17442393
Change-Id: I4d1e2357ab7e0d77dbcf09786f24ac5cc54160b9
1 file changed