Added extra safety in dexdump2 -d option around nonsense code.

Rationale:
Although it is hard to make this completely water tight against
"nonsense in", this extra safeguard prevents segfaulting on
run away instructions.

Bug: 72874888

Test: dexdump suite
Change-Id: Ida26dd8b2c96f7c0ad9600b57039ee6dddbc2526