DGIndex: Fix the judgment of the PMT check

Regression in the following commit.
Git HASH: 2b400c88f5b475e0811ba893d3b6d45a9ded367c
DGIndex: Remove the wrong code

It was unnecessary.
Git HASH: 2b400c88f5b475e0811ba893d3b6d45a9ded367c
Fix the bug that access the invalid area

The buffering of payload data was needed.
Git HASH: 2b400c88f5b475e0811ba893d3b6d45a9ded367c