patch 8.2.0399: various memory leaks

Problem:    Various memory leaks.
Solution:   Avoid the leaks. (Ozaki Kiichi, closes #5803)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index ca164cd..7193a2a 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -4188,6 +4188,7 @@
     if (win_split((int)p_cwh, WSP_BOT) == FAIL)
     {
 	beep_flush();
+	ga_clear(&winsizes);
 	return K_IGNORE;
     }
     cmdwin_type = get_cmdline_type();