Fix a bug of Figure.text() when "text" is a non-string array

[seisman]

Description of proposed changes

See #706 for the bug report.

We need to pass an string-type array to lib.virtualfile_from_vectors
function.

Closes #706.

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Notes

• You can write /format in the first line of a comment to lint the code automatically