a null move is not ok

[winapiadmin]

Describe the bug

chesslib/position.h

Lines 170 to 194 in 71907da

	template <bool RetAll = false> inline auto undoMove() -> std::conditional_t<RetAll, HistoryEntry<PieceC> &, void> {
	assert(!history.empty() && "undoMove called with empty history");
	// Restore previous state from history
	assert(current_state.mv.is_ok() && "Corrupted history entry");
	pieces_list[current_state.incr_sqs[0]] = current_state.incr_pc[0];
	pieces_list[current_state.incr_sqs[1]] = current_state.incr_pc[1];
	pieces_list[current_state.incr_sqs[2]] = current_state.incr_pc[2];
	pieces_list[current_state.incr_sqs[3]] = current_state.incr_pc[3];
	current_state = history.back();
	history.pop_back();
	if constexpr (RetAll) {
	return current_state;
	}
	return;
	}
	inline void doNullMove() {
	history.push_back(current_state);
	current_state.turn = ~current_state.turn;
	current_state.hash ^= zobrist::RandomTurn;
	current_state.fullMoveNumber += (current_state.turn == WHITE);
	current_state.pliesFromNull = current_state.repetition = 0;
	current_state.mv = Move::null();
	}

Minimal, Reproducible Example

#include <position.h>
int main(){Position p;p.doNullMove();p.undoMove();}

Partial test log

e.g. output from doctest/catch2 or your tester that's stripped to the failing test case

Full test log

Test log from the tester.

Hardware/Software info

List about the OS, hardware, compiler and tester.

Specifically, if the issue is reported by logic analysis, provide solution if applicable.

remove assert