patch 8.2.1049: Vim9: leaking memory when using continuation line

Problem:    Vim9: leaking memory when using continuation line.
Solution:   Keep a pointer to the continuation line in evalarg_T.  Centralize
            checking for a next command.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 4755a01..6c887fa 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2609,6 +2609,7 @@
 
 #ifdef FEAT_EVAL
     --ex_nesting_level;
+    vim_free(ea.cmdline_tofree);
 #endif
 
     return ea.nextcmd;
@@ -4912,7 +4913,7 @@
 	if (expr != NULL)
 	{
 	    ++emsg_off;
-	    p = eval_to_string(expr, NULL, FALSE);
+	    p = eval_to_string(expr, FALSE);
 	    --emsg_off;
 	    vim_free(expr);
 	}