Fix problems with project files and project directories

Now treat coherently the case when the project directory is removed from
the project directories.

data/core/init.lua

@@ -154,11 +154,11 @@ local function project_scan_thread()
             config.max_project_files.." files according to config.max_project_files.")
         end
         dir.files = t
+        core.redraw = true
+      end
       if dir.name == core.project_dir then
         include_project_dir = true
-          core.project_files = t
-        end
-        core.redraw = true
+        core.project_files = dir.files
       end
     end
     if not include_project_dir then

data/plugins/workspace.lua

@@ -168,12 +168,11 @@ local function load_workspace()
     if active_view then
       core.set_active_view(active_view)
     end
+    core.project_directories = {}
     for i, dir_name in ipairs(t.directories) do
-      if dir_name ~= "" then
       core.add_project_directory(system.absolute_path(dir_name))
     end
   end
-  end
 end