patch 8.2.4338: an error from an expression mapping messes up the display

Problem:    An error from an expression mapping messes up the display.
Solution:   When the expression results in an empty string return K_IGNORE.
            In cmdline mode redraw the command line. (closes #9726)
diff --git a/src/version.c b/src/version.c
index a02fefd..db2a923 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4338,
+/**/
     4337,
 /**/
     4336,