[cli] Write tags to config after successful verification

If a game has a `__required` SDL which is an empty string will fail verification
because the check for building the list of hashes will fail, implying that the
whole game including all the SDLs will be validated.

At the same time, if we are importing a game using a config file that doesn't
specify the `install_tags` for such a game, the install tags won't be saved
due to calling an early `exit(0)`.

These two issues combined can cause a verification, repair, verification loop.
This commit addresses both of those issues.

Related convertation on Discord:
https://discord.com/channels/695233346627698689/695234626582609940/1084939380713594924

legendary/cli.py

@@ -984,6 +984,10 @@ def install_game(self, args):
                 self.core.uninstall_tag(old_igame)
                 self.core.install_game(old_igame)
 
+            if old_igame.install_tags:
+                self.core.lgd.config.set(game.app_name, 'install_tags', ','.join(old_igame.install_tags))
+                self.core.lgd.save_config()
+
             # check if the version changed, this can happen for DLC that gets a version bump with no actual file changes
             if old_igame and old_igame.version != igame.version:
                 old_igame.version = igame.version
@@ -1225,7 +1229,7 @@ def verify_game(self, args, print_command=True, repair_mode=False, repair_online
                        key=lambda a: a.filename.lower())
 
         # build list of hashes
-        if config_tags := self.core.lgd.config.get(args.app_name, 'install_tags', fallback=None):
+        if config_tags := self.core.lgd.config.get(args.app_name, 'install_tags', fallback=None) is not None:
             install_tags = set(i.strip() for i in config_tags.split(','))
             file_list = [
                 (f.filename, f.sha_hash.hex())