Add a "No image" entry to the Page Editor's image dropdown

It heads the list and empties imageFileName; a widget with no image shows
it too.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ox_widget_properties.py

@@ -83,6 +83,7 @@ NUMERIC_FORMAT_TYPES = ("ontrolOx::NumericLabel", "ontrolOx::NumericLabelSet")
 BUF_ENCODING = "latin-1"
 
 IMAGE_EXTENSIONS = (".png", ".jpg", ".jpeg", ".bmp", ".bin")
+NO_IMAGE = "No image"      # the image list's entry for an empty imageFileName
 
 
 # --- value conversions ----------------------------------------------------------------
@@ -292,20 +293,24 @@ def image_names():
 def image_file_text(name):
     """An imageFileName value with its bank file's extension: 'trt' -> 'trt.jpg'.
 
-    A name no bank file matches is shown as it is.
+    A name no bank file matches is shown as it is, and an empty one as NO_IMAGE.
     """
-    if name:
-        for file_name in image_names():
-            if os.path.splitext(file_name)[0] == name:
-                return file_name
+    if not name:
+        return NO_IMAGE
+    for file_name in image_names():
+        if os.path.splitext(file_name)[0] == name:
+            return file_name
     return name
 
 
 def image_file_value(text):
     """The imageFileName value for a listed file: 'trt.jpg' -> 'trt'.
 
-    The slot holds the bare name, as the device looks the file up by it.
+    The slot holds the bare name, as the device looks the file up by it; NO_IMAGE
+    empties it.
     """
+    if text == NO_IMAGE:
+        return ""
     stem, ext = os.path.splitext(text.strip())
     return stem if ext.lower() in IMAGE_EXTENSIONS else text.strip()
 
@@ -900,15 +905,18 @@ class OxWidgetPropertiesPanel:
         self._bind_commit(entry, row)
         self._controls.append((entry, None))
 
-    def _bank_combo(self, cell, row, bank_values):
-        """A pick-only list filled from a bank each time it opens, the value kept listed."""
+    def _bank_combo(self, cell, row, bank_values, first=None):
+        """A pick-only list filled from a bank each time it opens, the value kept listed.
+
+        `first`, when given, heads the list: the entry for a slot naming nothing.
+        """
         var = row["var"]
 
         def fill():
-            values = bank_values()
+            values = ([first] if first else []) + bank_values()
             current = var.get()
             if current and current not in values:
-                values = [current] + values
+                values.insert(1 if first else 0, current)
             combo.configure(values=values)
 
         combo = ttk.Combobox(cell, textvariable=var, state="readonly", font=self._name_font,
@@ -926,7 +934,7 @@ class OxWidgetPropertiesPanel:
         return combo
 
     def _build_image(self, cell, row):
-        self._bank_combo(cell, row, image_names)
+        self._bank_combo(cell, row, image_names, first=NO_IMAGE)
 
     def _build_font(self, cell, row):
         self._bank_combo(cell, row, font_bank_names)