Ensure screen cannot draw during a term prompt

Fixes #2528

cmd/micro/micro.go

@@ -388,6 +388,7 @@ func DoEvent() {
 	var event tcell.Event
 
 	// Display everything
+	screen.DrawLock.Lock()
 	screen.Screen.Fill(' ', config.DefStyle)
 	screen.Screen.HideCursor()
 	action.Tabs.Display()
@@ -397,6 +398,7 @@ func DoEvent() {
 	action.MainTab().Display()
 	action.InfoBar.Display()
 	screen.Screen.Show()
+	screen.DrawLock.Unlock()
 
 	// Check for new events
 	select {

internal/screen/screen.go

@@ -24,6 +24,7 @@ var Events chan (tcell.Event)
 
 // The lock is necessary since the screen is polled on a separate thread
 var lock sync.Mutex
+var DrawLock sync.Mutex
 
 // drawChan is a channel that will cause the screen to redraw when
 // written to even if no event user event has occurred
@@ -120,6 +121,7 @@ func TempFini() bool {
 	if !screenWasNil {
 		Screen.Fini()
 		Lock()
+		DrawLock.Lock()
 		Screen = nil
 	}
 	return screenWasNil
@@ -130,6 +132,7 @@ func TempStart(screenWasNil bool) {
 	if !screenWasNil {
 		Init()
 		Unlock()
+		DrawLock.Unlock()
 	}
 }