`get_dotnet_table_row` used `if row_index - 1 <= 0` to guard against invalid
indices. Because .NET metadata tables are 1-indexed, row_index=1 is the first
valid row, but the condition is equivalent to `row_index <= 1`, silently
rejecting it and making the first row of every table unreachable.
Changed to `if row_index <= 0`, which correctly rejects only the zero/null
token and leaves all valid rows accessible. Added four unit tests against the
real dd9098ff91717f4906afe9dafdfa2f52.exe_ sample to verify the guard
boundary: row_index=1 returns the first row, row_index=0 returns None, all
row indices 1..N succeed, and an out-of-bounds index returns None.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
