schema compile amend UPDATE explicit check for coverity
diff --git a/src/schema_compile_amend.c b/src/schema_compile_amend.c
index cf509c7..8593de8 100644
--- a/src/schema_compile_amend.c
+++ b/src/schema_compile_amend.c
@@ -274,6 +274,8 @@
 {
     struct lysp_stmt *ch;
 
+    assert(!*child);
+
     LY_LIST_FOR(orig_child, orig_child) {
         /* new child */
         if (!*child) {