Added check to ensure we are in lighttable view prior to callling

darktable.register_lib.  If darktable was invoked in single
image (darkroom) mode, then an event handler is registered to
detect the change from darkroom mode to lighttable mode so that
we can then call darktable.register_lib.

tools/script_manager.lua

@@ -450,6 +450,26 @@ local function link_downloads_directory()
   os.execute("ln -s " .. "$HOME/Downloads " .. LUA_DIR .. "/downloads")
 end
 
+local function install_module()
+  if not sm.module_installed then
+    dt.register_lib(
+      "script_manager",     -- Module name
+      "script manager",     -- Visible name
+      true,                -- expandable
+      false,               -- resetable
+      {[dt.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_LEFT_CENTER", 0}},   -- containers
+      dt.new_widget("box") -- widget
+      {
+        orientation = "vertical",
+        sm.main_box,
+      },
+      nil,-- view_enter
+      nil -- view_leave
+    )
+    sm.module_installed = true
+  end
+end
+
 -- - - - - - - - - - - - - - - - - - - - - - - - 
 -- M A I N  P R O G R A M
 -- - - - - - - - - - - - - - - - - - - - - - - - 
@@ -466,6 +486,8 @@ sm.script_names = {}
 sm.script_paths = {}
 sm.main_menu_choices = {}
 sm.main_stack_items = {}
+sm.event_registered = false
+sm.module_installed = false
 
 -- see if we've run this before
 
@@ -742,21 +764,21 @@ sm.main_box = dt.new_widget("box"){
 -- D A R K T A B L E  I N T E G R A T I O N 
 -- - - - - - - - - - - - - - - - - - - - - - - - 
 
--- register the module
-dt.register_lib(
-  "script_manager",     -- Module name
-  "script manager",     -- Visible name
-  true,                -- expandable
-  false,               -- resetable
-  {[dt.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_LEFT_CENTER", 0}},   -- containers
-  dt.new_widget("box") -- widget
-  {
-    orientation = "vertical",
-    sm.main_box,
-  },
-  nil,-- view_enter
-  nil -- view_leave
-)
+if dt.gui.current_view().name == "lighttable" then
+  install_module()
+else
+  if not sm.event_registered then
+    dt.register_event(
+      "view-changed",
+      function(event, old_view, new_view)
+        if new_view.name == "lighttable" and old_view.name == "darkroom" then
+          install_module()
+         end
+      end
+    )
+    sm.event_registered = true
+  end
+end
 
 -- set up the scripts block if we have them otherwise we'll wait until we download them