org-paste-subtree: Do not leave empty line in place of level indicator

* lisp/org.el (org-paste-subtree): Remove the whole line when level
indicator is provided.  Improve check for level indicator.
* testing/lisp/test-org.el (test-org/paste-subtree): Add test.

Reported-by: Philipp Kiefer <phil.kiefer@gmail.com>
Link: https://orgmode.org/list/a2cc49d3-7f65-5f6a-8f05-21e5056335b3@gmail.com

lisp/org.el

@@ -7100,6 +7100,7 @@ When REMOVE is non-nil, remove the subtree from the clipboard."
 	    (old-level (if (string-match org-outline-regexp-bol txt)
 			   (- (match-end 0) (match-beginning 0) 1)
 		         -1))
+            level-indicator?
 	    (force-level
 	     (cond
 	      (level (prefix-numeric-value level))
@@ -7107,7 +7108,7 @@ When REMOVE is non-nil, remove the subtree from the clipboard."
 	      ;; headline, use the number of stars as the forced level.
 	      ((and (org-match-line "^\\*+[ \t]*$")
 		    (not (eq ?* (char-after))))
-	       (org-outline-level))
+	       (setq level-indicator? (org-outline-level)))
 	      ((looking-at-p org-outline-regexp-bol) (org-outline-level))))
 	    (previous-level
 	     (save-excursion
@@ -7129,8 +7130,8 @@ When REMOVE is non-nil, remove the subtree from the clipboard."
 	    (org-odd-levels-only nil)
 	    beg end newend)
        ;; Remove the forced level indicator.
-       (when (and force-level (not level))
-         (delete-region (line-beginning-position) (point)))
+       (when level-indicator?
+         (delete-region (line-beginning-position) (line-beginning-position 2)))
        ;; Paste before the next visible heading or at end of buffer,
        ;; unless point is at the beginning of a headline.
        (unless (and (bolp) (org-at-heading-p))

testing/lisp/test-org.el

@@ -8617,6 +8617,19 @@ CLOSED: %s
 	  (org-test-with-temp-text "*** <point>"
 	    (org-paste-subtree nil "* Text")
 	    (buffer-string))))
+  ;; Remove the indicator line completely.
+  (should
+   (equal "* Top
+text
+more text
+*** Text
+"
+	  (org-test-with-temp-text "* Top
+text
+*** <point>
+more text"
+	    (org-paste-subtree nil "* Text")
+	    (buffer-string))))
   ;; Optional argument LEVEL forces a level for the subtree.
   (should
    (equal "* H\n*** Text\n"