Allow empty template when inserting checklists to Org item

In some cases, the backlinks may be sufficient as checklist.

site-lisp/db-org.el

@@ -849,43 +849,14 @@ The template is determined by the TEMPLATE_ID property, which
 must be an ID referencing the proper template item.  If that
 property is not set, search for the topmost sibling of the
 current item and see whether its headline is matching
-\"^Template.*\"; if so, use its body as template, and barf
+\"^Template.*\"; if so, use its body as template."
-otherwise."
   (interactive)
 
   (unless (derived-mode-p 'org-mode)
     (user-error "Not in Org mode, aborting"))
 
-  (let (template-pom)
+  ;; Insert relevant backlinks, when available.
-
+  (let ((parent-depth (--when-let (org-entry-get (point) "CHECKLIST_BACKLINK_DEPTH" nil)
-    ;; Check for TEMPLATE_ID property
-    (when-let ((template-id (org-entry-get (point) "TEMPLATE_ID")))
-      (setq template-pom (org-id-find template-id :get-marker))
-      (unless template-pom
-        (warn "TEMPLATE_ID is set, but could not be resolved: %s"
-              template-id)))
-
-    ;; If no template has been found so far, search for top-most sibling and
-    ;; whether its headline starts with “Template”; use that when found.
-    (unless template-pom
-      (let ((top-most-sibling (condition-case _
-                                  (save-restriction
-                                    (save-mark-and-excursion
-                                      (outline-up-heading 1 'invisible-ok)
-                                      (outline-next-heading)
-                                      (point)))
-                                (t nil))))
-        (when (and top-most-sibling
-                   (integerp top-most-sibling) ; just to make sure we have a
-                                               ; point here
-                   (string-match-p "^Template.*"
-                                   (org-entry-get top-most-sibling "ITEM")))
-          (setq template-pom top-most-sibling))))
-
-    (unless template-pom
-      (user-error "Cannot find template via TEMPLATE_ID property or top-most sibling"))
-
-    (let ((parent-depth (--when-let (org-entry-get (point) "CHECKLIST_BACKLINK_DEPTH" nil)
                           (string-to-number it)))
           number-of-backlinks
           point-before-backlinks)
@@ -915,8 +886,38 @@ otherwise."
         (delete-region point-before-backlinks (point))
         (insert " none.")))
 
-    (insert "\n\nTemplate:\n")
+  ;; Insert template, when avilable.
-    (db/org-copy-body-from-item-to-point template-pom)))
+  (let (template-pom)
+
+    (insert "\n\nTemplate:")
+
+    ;; Check for TEMPLATE_ID property
+    (when-let ((template-id (org-entry-get (point) "TEMPLATE_ID")))
+      (setq template-pom (org-id-find template-id :get-marker))
+      (unless template-pom
+        (warn "TEMPLATE_ID is set, but could not be resolved: %s"
+              template-id)))
+
+    ;; If no template has been found so far, search for top-most sibling and
+    ;; whether its headline starts with “Template”; use that when found.
+    (unless template-pom
+      (let ((top-most-sibling (condition-case _
+                                  (save-restriction
+                                    (save-mark-and-excursion
+                                      (outline-up-heading 1 'invisible-ok)
+                                      (outline-next-heading)
+                                      (point)))
+                                (t nil))))
+        (when (and top-most-sibling
+                   (integerp top-most-sibling) ; just to make sure we have a point here
+                   (string-match-p "^Template.*"
+                                   (org-entry-get top-most-sibling "ITEM")))
+          (setq template-pom top-most-sibling))))
+
+    (if (not template-pom)
+        (insert " none.")
+      (insert "\n")
+      (db/org-copy-body-from-item-to-point template-pom))))
 
 (define-obsolete-function-alias 'db/org-copy-template
     'db/org-insert-checklist