Return AVIF_RESULT_TRUNCATED_DATA if a file-level box is truncated
diff --git a/src/read.c b/src/read.c
index 3407bdd..b40adff 100644
--- a/src/read.c
+++ b/src/read.c
@@ -2063,7 +2063,7 @@
             }
             if (boxContents.size != header.size) {
                 // A truncated box, bail out
-                return AVIF_RESULT_BMFF_PARSE_FAILED;
+                return AVIF_RESULT_TRUNCATED_DATA;
             }
         }