Make fzf immediately quit when failed to read /dev/tty

Close #798

src/tui/tui.go

@@ -1,6 +1,7 @@
 package tui
 
 import (
+	"os"
 	"strconv"
 	"time"
 )
@@ -275,6 +276,10 @@ func EmptyTheme() *ColorTheme {
 		Border:       colUndefined}
 }
 
+func errorExit() {
+	os.Exit(2)
+}
+
 func init() {
 	Default16 = &ColorTheme{
 		Fg:           colDefault,