Suspicious check in `UniTensor::put_block()`

[ianmccul]

This code is very suspicious:

Cytnx/include/UniTensor.hpp

Lines 1497 to 1505 in fa4596e

	if (b < 0) {
	if (check) {
	cytnx_error_msg(true,
	"[ERROR][put_block][BlockUniTensor] no avaliable block exists, "
	"check=true, so error throws. \n If you want without error when block "
	"is not avaliable, set check=false.%s",
	"\n");
	}
	} else {

This is replacing a block of a UniTensor, but if the caller specifies check = false then it silently ignores the error if the block to replace doesn't exist. What is the use case for this?

[yingjerkao]

Looking at the revision history, this seems to exist from the beginning. The error should be thrown regardless.

[manuschneider]

I can only guess that this was in similarity with the force option of get_block. There, if force = true, the function does not raise an error if no valid block exists, but returns an empty tensor. I might see a usecase here (check if the output is empty and treat that case accordingly).
But for put_block I do not see why a force option would be desired - the user should make sure the block to put is not empty. Moreover, the user interface exposed this option as force, where one would assume that true corresponds to no checks, but internally it is called check, and the checks actually only happen if the option is true.
Since no one seemed to have noticed this inconsistency, I conclude that it was not used (why would it be?). So I just removed it in #702.