CatalogueUI : Fix update when first image added and last image removed

In this case, the `index` plug doesn't change value, but whether or not it maps to an actual image does change. And we use that mapping in `_updateFromValues()`, so the first image added wasn't connected to the `__descriptionWidget` and `__nameWidget`, and the last image removed wasn't disconnected.

Changes.md

@@ -22,7 +22,9 @@ Fixes
 - WidgetAlgo : Fixed issue preventing `grab()` from capturing popup menus on Windows.
 - ShowURL : Fixed opening of "file://" URLs on Windows (#5861).
 - Shader : Fixed "Revert to Defaults" menu item in NodeEditor (#1862).
-- Catalogue : Fixed bug which allowed locked Catalogues to be edited.
+- Catalogue :
+  - Fixed bug which allowed locked Catalogues to be edited.
+  - Fixed NodeEditor update when the first image is added or the last image is removed.
 - NameWidget : Fixed bug which allowed plugs on locked nodes to be renamed.
 
 API

python/GafferImageUI/CatalogueUI.py

@@ -753,6 +753,9 @@ def __init__( self, plug, **kw ) :
 				self.__pathListing.dropSignal().connect(
 					Gaffer.WeakMethod( self.__pathListingDrop ), scoped = False
 				)
+				self.__pathListing.getPath().pathChangedSignal().connect(
+					Gaffer.WeakMethod( self.__pathChanged ), scoped = False
+				)
 				self.keyPressSignal().connect( Gaffer.WeakMethod( self.__keyPress ), scoped = False )
 
 				with GafferUI.ListContainer( GafferUI.ListContainer.Orientation.Horizontal, spacing = 4 ) as self.__buttonRow :
@@ -838,6 +841,12 @@ def _updateFromEditable( self ) :
 		# `self.__descriptionWidget` because they deal with that
 		# internally.
 
+	def __pathChanged( self, path ) :
+
+		# `_updateFromValues()` is sensitive to the contents of the image path so
+		# we need to do an update when it changes.
+		self._requestUpdateFromValues()
+
 	def __plugMetadataValueChanged( self, plug, key, reason ) :
 
 		if key == _columnsMetadataKey and plug == self.getPlug() :