Bugfixes to stabilize latest application version

[HackXIt]

• File selection doesn't actually open file 908b0e9
• Lockfile was not properly update to use latest kivyMD 4eaf020
• fbind error if selected API is actually None and settings attempts to add it c915298
• Use lazy formatting on all calls to log functions d5c126c

[deinhofer]

When opening file the self.opened_file is not set correctly:

It should be the following, otherwise a subsequent save action does not work:

        if self.last_path is not None and os.path.isfile(os.path.join(self.last_path, self.opened_file)):
            self.opened_file = os.path.join(self.last_path, self.opened_file)
            self.load_textfile(self.opened_file)

[deinhofer]

When opening failed due to unsupported file type, everything should be reset:
e.g.:

    def load_textfile(self, file: str):
        file_ext = file.split('.')[-1]
        if file_ext not in self.supported_text_files:
            # if file extension is not supported, don't try to open it and reset everything
            self.opened_file = None
            self.ids.text_main.text = ""
            log.error(f"{self.__class__.__name__}: Unsupported file type: {file_ext}")

[deinhofer]

When clicking on ExampleAPI, the screen does not open:

[deinhofer]

ok, thanks. I will merge it for now, so that the students can already work on it.
But please continue to commit, if you have a new fix.