Fix missing checkbox image for unchecked required kit

The boxes dict was missing the (False, False) key — an unchecked kit
that is also required — which caused a KeyError when the Kit Manager
opened automatically for files with incomplete checksums.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.065"
+VERSION = "0.0.0.066"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True

manage_kits.py

@@ -238,6 +238,7 @@ class KitsPanel:
             (True, True): make_checkbox_image(True, True),
             (False, True): make_checkbox_image(False, True),
             (True, False): make_checkbox_image(True, False),
+            (False, False): make_checkbox_image(False, False),
         }
 
         hint = ttk.Label(