patch 8.2.2137: Vim9: :echo and :execute give error for empty argument

Problem:    Vim9: :echo and :execute give error for empty argument.
Solution:   Ignore an empty argument. (closes #7468)
diff --git a/src/version.c b/src/version.c
index 0cb1d92..64391b4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2137,
+/**/
     2136,
 /**/
     2135,