Unicode replacement char for non-displayable chars

internal/screen/screen.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"sync"
+	"unicode"
 
 	"github.com/zyedidia/micro/v2/internal/config"
 	"github.com/zyedidia/micro/v2/internal/util"
@@ -97,6 +98,10 @@ func ShowCursor(x, y int) {
 // SetContent sets a cell at a point on the screen and makes sure that it is
 // synced with the last cursor location
 func SetContent(x, y int, mainc rune, combc []rune, style tcell.Style) {
+	if !unicode.IsPrint(mainc) {
+		mainc = '<27>'
+	}
+
 	Screen.SetContent(x, y, mainc, combc, style)
 	if util.FakeCursor && lastCursor.x == x && lastCursor.y == y {
 		lastCursor.r = mainc