patch 8.2.1293: Vim9: error when using vim9script in TextYankPost

Problem:    Vim9: error when using vim9script in TextYankPost.
Solution:   Use EX_LOCKOK instead of the EX_CMDWIN flag for command that can
            be used when text is locked. (closes #6529)

src/vim9compile.c

@@ -3755,7 +3755,9 @@ compile_subscript(
 	    }
 	}
 
-	if (*p == '(')
+	// Do not skip over white space to find the "(", "exeucte 'x' ()" is
+	// not a function call.
+	if (**arg == '(')
 	{
 	    garray_T    *stack = &cctx->ctx_type_stack;
 	    type_T	*type;