Code does not exit even when errors are encountered

[wenfei-li]

Describe the bug

I have noticed that, if users set init_chg file but do not provide the required charge density files, the program will not report error and exit. Instead, it will continue with density initialized using atomic densities. The user will then get results that are not what they intend to have.
See below for the code responsible for this behaviour.

Expected behavior

exit the code with error, or at least give users an option to decide what would be the behaviour they want.

To Reproduce

No response

Environment

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Additional Context

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[pxlxingliang]

The earlier abacus will quit when init_chg=file when reading file failed, but since #3264, it is changed to use atomic charge if reading file failed.
It seems, abacus should support these two contradictory functions, and I suggest adding a new option auto for init_chg, and modify option file:

• file: abacus try to read charge from file, and if reading is failed, abacus will warning quit.
• auto: abacus firstly read charge from file, and if reading is filed, abacus will use atomic charge and keep running.