Fix warnings (LOG_LEVEL_WARN) about alias not found for deleted resources

(cherry picked from commit d3d4cd93ac2ca18d68f67ec5a145f94dafaa49b6)

Conflicts:
	core/model/modx/processors/resource/getnodes.class.php
Need some sleep...

(cherry picked from commit 203b42c95a5b784c9d094ea52b8723c70fc676b0)
Fix warnings (LOG_LEVEL_WARN) about alias not found for deleted resources

Merge branch 'pr/794' into develop

* pr/794:
  Need some sleep...
  Fix warnings (LOG_LEVEL_WARN) about alias not found for deleted resources
Handle "preview" resource button visibility according to the "deleted" status of the resource

(cherry picked from commit 18840d793e31d200cb8a653f65a821525a610418)

Conflicts:
	manager/assets/modext/widgets/resource/modx.panel.resource.js
	manager/assets/modext/widgets/resource/modx.tree.resource.js