Ensure we never access out of range table dividers, fixes #2018 (#2026)

ensure we never access out of range table dividers

widget/table.go

@@ -330,7 +330,7 @@ func (t *tableRenderer) moveIndicators() {
 
 	divs := 0
 	i := minCol
-	for x := offX + visibleColWidths[i]; i < minCol+colDivs; x += visibleColWidths[i] + separatorThickness {
+	for x := offX + visibleColWidths[i]; i < minCol+colDivs && divs < len(t.dividers); x += visibleColWidths[i] + separatorThickness {
 		i++
 
 		t.dividers[divs].Move(fyne.NewPos(theme.Padding()+x-t.scroll.Offset.X, theme.Padding()))
@@ -341,7 +341,7 @@ func (t *tableRenderer) moveIndicators() {
 
 	i = 0
 	count := int(t.scroll.Offset.Y) % int(t.cellSize.Height+separatorThickness)
-	for y := theme.Padding() + t.scroll.Offset.Y - float32(count) - separatorThickness; y < t.scroll.Offset.Y+t.t.size.Height && i < rows-1; y += t.cellSize.Height + separatorThickness {
+	for y := theme.Padding() + t.scroll.Offset.Y - float32(count) - separatorThickness; y < t.scroll.Offset.Y+t.t.size.Height && i < rows-1 && divs < len(t.dividers); y += t.cellSize.Height + separatorThickness {
 		if y < theme.Padding()+t.scroll.Offset.Y {
 			continue
 		}

widget/table_test.go

@@ -303,3 +303,32 @@ func TestTable_ShowVisible(t *testing.T) {
 	cellRenderer.Refresh()
 	assert.Equal(t, 8, len(cellRenderer.Objects()))
 }
+
+func TestTable_SeparatorThicknessZero_NotPanics(t *testing.T) {
+	test.NewApp()
+	defer test.NewApp()
+
+	test.ApplyTheme(t, &separatorThicknessZeroTheme{test.Theme()})
+
+	table := NewTable(
+		func() (int, int) { return 500, 150 },
+		func() fyne.CanvasObject {
+			return NewLabel("placeholder")
+		},
+		func(TableCellID, fyne.CanvasObject) {})
+
+	assert.NotPanics(t, func() {
+		table.Resize(fyne.NewSize(400, 644))
+	})
+}
+
+type separatorThicknessZeroTheme struct {
+	fyne.Theme
+}
+
+func (t *separatorThicknessZeroTheme) Size(n fyne.ThemeSizeName) float32 {
+	if n == theme.SizeNameSeparatorThickness {
+		return 0
+	}
+	return t.Theme.Size(n)
+}