Move SSD PDF tree guard to typed Kotlin

ober

b4a3657158ebc3806cc05f7548a5fa7d4735d070

diff --git a/templates/ssd-review.ss b/templates/ssd-review.ss
index 999cf50..370cf10 100644
--- a/templates/ssd-review.ss
+++ b/templates/ssd-review.ss
@@ -7428,7 +7428,9 @@
        "    }"
        ""
        "    private fun findSsdPdfsFromTree(treeUri: Uri): List<SsdPdfChoice> {"
-       "        val root = DocumentFile.fromTreeUri(this, treeUri) ?: return emptyList()"
+       "        val maybeRoot = DocumentFile.fromTreeUri(this, treeUri)"
+       "        if (!documentFilePresent(maybeRoot)) return emptyList()"
+       "        val root = checkNotNull(maybeRoot)"
        "        return findSsdPdfs(root)"
        "    }"
        ""