ui/text: use default colors to guard against empty materials

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/text/editor.go

@@ -4,6 +4,7 @@ package text
 
 import (
 	"image"
+	"image/color"
 	"math"
 	"time"
 	"unicode/utf8"
@@ -203,9 +204,12 @@ func (e *Editor) Layout(ops *ui.Ops, cs layout.Constraints) layout.Dimens {
 		Offset:    off,
 	}
 	ui.PushOp{}.Add(ops)
+	// Apply material. Set a default color in case the material is empty.
 	if e.rr.len() > 0 {
+		draw.ColorOp{Col: color.RGBA{A: 0xff}}.Add(ops)
 		e.Material.Add(ops)
 	} else {
+		draw.ColorOp{Col: color.RGBA{A: 0xaa}}.Add(ops)
 		e.HintMaterial.Add(ops)
 	}
 	for {