The functions that do not have checks on whether the font exists or not have been pre-checked by me. You can look through https://github.com/SFML/SFML/blob/master/src/SFML/Graphics/Text.cpp to view which methods are safe to perform while the font is dead. They follow the same principle. They set a boolean, m_geometryNeedUpdate, to true and perform the transformations later on (for instance during draw). This PR shouldn't have any reason for UB.
The functions that do not have checks on whether the font exists or not have been pre-checked by me. You can look through https://github.com/SFML/SFML/blob/master/src/SFML/Graphics/Text.cpp to view which methods are safe to perform while the font is dead. They follow the same principle. They set a boolean, m_geometryNeedUpdate, to true and perform the transformations later on (for instance during draw). This PR shouldn't have any reason for UB.