cleaned up the source_lookup

src/source.re.c

@@ -179,7 +179,7 @@ const struct source *source_lookup(struct sources *const s,
 	it = source_tree_less(&s->dates, x);
 	/* If it's before all elements of the journal or is not on the same date as
 	 the source, this has no source, which is `list[0]` by <fn:sources>. */
-	if(!source_tree_has_element(&it)
-		|| x.date.u32 != source_tree_key(&it).date.u32) return s->list.data + 0;
-	return s->list.data + *source_tree_value(&it);
+	return s->list.data + (source_tree_has_element(&it)
+		&& x.date.u32 == source_tree_key(&it).date.u32
+		? *source_tree_value(&it) : 0);
 }