patch 8.2.3337: completing "call g:" returns entries with just "g:"

Problem:    Completing "call g:" returns entries with just "g:". (Naohiro Ono)
Solution:   Skip empty strings returned by get_user_func_name(). (closes #8753)

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3337,
 /**/
     3336,
 /**/