PathFilterUI : Fix Select Affected Objects on PathFilter.paths cells

This appears to have been broken as far back as 1.2.0.0.

File "/opt/gaffer-1.2.0.0-linux/python/GafferSceneUI/PathFilterUI.py", line 213, in __popupMenu
	selection = IECore.PathMatcher( plugValueWidget.vectorDataWidget().getData()[0] )
IndexError: list index out of range

Changes.md

@@ -10,6 +10,7 @@ Fixes
 - PathFilter :
   - Fixed bug preventing display of "Select Affected Objects" menu item in the row name column of promoted Spreadsheets.
   - Fixed bug preventing use of "Select Affected Objects" menu item in the row name column of Spreadsheets with `enabledRowNames` connected to the `paths` plug of a PathFilter.
+  - Fixed error when using "Select Affected Objects" on Spreadsheet cells connected to the `paths` plug of a PathFilter.
 
 1.4.15.3 (relative to 1.4.15.2)
 ========

python/GafferSceneUI/PathFilterUI.py

@@ -205,7 +205,7 @@ def __popupMenu( menuDefinition, plugValueWidget ) :
 			if cellPlug is None :
 				return
 
-			selection = IECore.PathMatcher( plugValueWidget.vectorDataWidget().getData()[0] )
+			selection = IECore.PathMatcher( plug.getValue() )
 
 		elif plug == rowPlug["name"] and spreadsheet["selector"].getValue() == "${scene:path}" :
 			selection = IECore.PathMatcher( [ plugValueWidget.getPlug().getValue() ] )