cmd/geth, core/rawdb: add missing error checks (#19871)

* Added missing error checks

Add error handling where we assign err a value, but don't check for it being nil.

* core/rawdb: tiny style nit

cmd/geth/retesteth.go

@@ -533,6 +533,9 @@ func (api *RetestethAPI) mineBlock() error {
 		}
 	}
 	block, err := api.engine.FinalizeAndAssemble(api.blockchain, header, statedb, txs, []*types.Header{}, receipts)
+	if err != nil {
+		return err
+	}
 	return api.importBlock(block)
 }