scribble: fix list splicing for sections

original commit: 570f51e942d3668727f7534c92e18837697d8e96

pkgs/scribble-pkgs/scribble-lib/scribble/decode.rkt

@@ -245,9 +245,13 @@
                           (part-to-collect part)
                           para
                           (cons s (part-parts part))))
-             (if (splice? (car l))
-               (loop (append (splice-run (car l)) (cdr l)) s-accum)
-               (loop (cdr l) (cons (car l) s-accum))))))]
+             (cond
+              [(splice? (car l))
+               (loop (append (splice-run (car l)) (cdr l)) s-accum)]
+              [(list? (car l))
+               (loop (append (car l) (cdr l)) s-accum)]
+              [else
+               (loop (cdr l) (cons (car l) s-accum))]))))]
       [(splice? (car l))
        (loop (append (splice-run (car l)) (cdr l))
              next? keys colls accum title tag-prefix tags vers style)]

pkgs/scribble-pkgs/scribble-test/tests/scribble/docs/list-section.scrbl

@@ -0,0 +1,9 @@
+#lang scribble/base
+
+@title{A}
+
+@section{B}
+
+@(list @subsection{C})
+
+@(list @subsection{D})

pkgs/scribble-pkgs/scribble-test/tests/scribble/docs/list-section.txt

@@ -0,0 +1,9 @@
+A
+
+1. B
+
+1.1. C
+
+
+1.2. D
+