patch 8.2.4842: expand("%:p") is not empty when there is no buffer name

Problem:    expand("%:p") is not empty when there is no buffer name.
Solution:   When ignoring errors still return NULL. (closes #10311)
diff --git a/src/version.c b/src/version.c
index 31306fb..0d95a7c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4842,
+/**/
     4841,
 /**/
     4840,