[Backwards-compatibility] p.keeper.GetVersion() -> p.version to not panic when from ParseMemo (which has a nil keeper)

[Backwards-compatibility (Version-unspecific)]

Intended to close #1945 (closed)
'[Backwards-compatibility] Block 11783100 sync failure with v1.130.0-v1.124.0 (but not v1.123.0) THORNodes'.

(After running for a while, the v1.130.0-f45ae430 fullnode has reached height 12110000
(by which point already v1.118.0)
without further sync failure;
I plan to continue its syncing until either an expected sync failure at v1.131.0 or any earlier unexpected sync failure.)