[CBR-482] dropObftEbb: don't roll back genesis out of existence during startup

Discusion in: https://iohk.myjetbrains.com/youtrack/issue/CBR-482

Author: deepfire

lib/src/Pos/Worker/Block.hs

@@ -211,7 +211,7 @@ dropObftEbb genesisConfig txpConfig = do
     tipHeader <- DB.getTipHeader
     case tipHeader of
         BlockHeaderMain _      -> pure ()
-        BlockHeaderGenesis _   -> do
+        BlockHeaderGenesis _   -> unless (tipHeader ^. epochIndexL == 0) $ do
             mbEbbBlund <- getBlund (configGenesisHash genesisConfig)
                                    (blockHeaderHash tipHeader)
             case mbEbbBlund of