Fix SIN v1/v2 files always falling through to v4 parser

[frankfrot30]

Summary

• SinFile's constructor checked version==1, version==2, version==3 as three independent if statements instead of an if / else if chain.
• Only the version==3 check had an else branch (which attempts v4/tar-gzip parsing).
• As a result, any file with version==1 or version==2 was parsed correctly and then immediately re-parsed by the v4 branch, which always fails with "Not a sin file" since v1/v2 sin files are not tar/gzip archives.
• This breaks flashing for every device using SIN v1/v2 packages, i.e. the whole 2011-2012 Xperia line (X10, arc, ray, S, P, U, sola, acro, etc.).

Fix

Changed the two independent if statements to else if, so v4 parsing is only attempted when the version byte doesn't match 1, 2, or 3.

Test plan

• Confirmed the bug: read the raw bytes of a Sony Xperia U (ST25i) loader.sin from an official FTF, first byte is 0x02 (SIN v2).
• Reproduced "Not a sin file" / "Error flashing. Aborted" with the original code during a real flash attempt on an ST25i in flashmode.
• Applied the fix, rebuilt (Flashtool:compileJava), ran from source (Flashtool:run), and confirmed the ST25i firmware now flashes successfully past the loader stage.