patch 8.1.1594: may still start file dialog while exiting

Problem:    May still start file dialog while exiting.
Solution:   Ignore the "browse" modifier in another place when exiiting.
            (Ozaki Kiichi, closes #4582)
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 0eaa662..4126fe0 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -3818,7 +3818,7 @@
     else
     {
 #ifdef FEAT_BROWSE
-	if (cmdmod.browse)
+	if (cmdmod.browse && !exiting)
 	{
 	    if (
 # ifdef FEAT_GUI