Add missing list double click handler.

Projects/Src/IDE.SignToolsForm.dfm

@@ -38,6 +38,7 @@ object SignToolsForm: TSignToolsForm
       ItemHeight = 13
       TabOrder = 0
       OnClick = SignToolsListBoxClick
+      OnDblClick = SignToolsListBoxDblClick
     end
     object AddButton: TButton
       Left = 480

Projects/Src/IDE.SignToolsForm.pas

@@ -29,6 +29,7 @@ type
     procedure AddButtonClick(Sender: TObject);
     procedure RemoveButtonClick(Sender: TObject);
     procedure EditButtonClick(Sender: TObject);
+    procedure SignToolsListBoxDblClick(Sender: TObject);
   private
     FSignTools: TStringList;
     procedure CommandDocImageClick(Sender: TObject);
@@ -185,4 +186,10 @@ begin
   UpdateSignToolsButtons;
 end;
 
+procedure TSignToolsForm.SignToolsListBoxDblClick(Sender: TObject);
+begin
+  if EditButton.Enabled then
+    EditButton.Click;
+end;
+
 end.