isoInstaller: fix interactive (no-kickstart) ISO install

Booting the ISO interactively (no ks= boot param, no -c config, no VMware
guestinfo.kickstart.*) was broken by two coupled regressions:

1) _load_ks_config_platform()/_load_ks_config_vmware() returned None when
   no platform kickstart exists; __init__ then crashed at
   'if "live" not in install_config' with:
       TypeError: argument of type 'NoneType' is not a container or iterable
   Fix: return an empty {} config instead of None.

2) The 'live' block unconditionally stamped install_config['live']=True,
   making the empty interactive config truthy. installer.configure() only
   runs the UI configurator when 'not install_config', so the UI was
   skipped and _check_install_config() raised 'No disk configured'.
   Fix: only stamp 'live' on a non-empty (kickstart) config; leave the
   interactive config empty so the UI runs (live then defaults via
   _add_defaults()).

Regression introduced by 9fc8733 on top of 0a72c3a.

Co-Authored-By: Daniel Casota <dcasota@gmail.com>

Author: dcasota

photon_installer/isoInstaller.py

@@ -79,8 +79,12 @@ def __init__(self, options, params={}):
         else:
             install_config = self._load_ks_config_platform(verify=not insecure_installation)
 
-        # 'live' should be True for iso installs
-        if 'live' not in install_config:
+        # 'live' should be True for iso installs. Only stamp it on an actual
+        # (non-empty) kickstart config. For an interactive install the config
+        # is empty here and must stay falsy, otherwise installer.configure()
+        # ('if not install_config and ui_config') skips the UI configurator
+        # and _check_install_config() fails with "No disk configured".
+        if install_config and 'live' not in install_config:
             install_config['live'] = True
 
         if insecure_installation and install_config is not None:
@@ -164,7 +168,10 @@ def _load_ks_config_platform(self, verify=True):
         if CommandUtils.is_vmware_virtualization():
             return self._load_ks_config_vmware(verify=verify)
         else:
-            return None
+            # No platform-provided kickstart: fall back to an interactive
+            # install with an empty config. Returning None here makes the
+            # caller crash at "if 'live' not in install_config".
+            return {}
 
     def _load_ks_config_vmware(self, verify=True):
         try:
@@ -191,6 +198,10 @@ def _load_ks_config_vmware(self, verify=True):
             print(
                 f"Failed to run vmtoolsd, do you have open-vm-tools installed? Error: {e}"
             )
+        # No guestinfo kickstart (data/url both absent) or vmtoolsd missing:
+        # fall back to an interactive install with an empty config instead of
+        # returning None, which would crash at "if 'live' not in install_config".
+        return {}
 
     def mount_media(self, photon_media, mount_path=Defaults.MOUNT_PATH):
         """Mount the external media"""