defensive nil checks around CanvasForObject

ui/browsing/browsingpane.go

@@ -152,7 +152,7 @@ func (b *BrowsingPane) doSetPage(p Page) bool {
 	}
 	// TODO: reset focus only if something inside the previous page had focus
 	if c := fyne.CurrentApp().Driver().CanvasForObject(b); c != nil {
-		c.Focus(nil)
+		c.Unfocus()
 	}
 	b.curPage = p
 	if np, ok := p.(CanShowNowPlaying); ok {

ui/browsing/playlistpage.go

@@ -392,7 +392,9 @@ func NewPlaylistPageHeader(page *PlaylistPage) *PlaylistPageHeader {
 		}
 		buttonRow.Objects[3] = searchEntry
 		searchEntry.SetMinWidth(minW)
-		fyne.CurrentApp().Driver().CanvasForObject(a).Focus(searchEntry)
+		if c := fyne.CurrentApp().Driver().CanvasForObject(a); c != nil {
+			c.Focus(searchEntry)
+		}
 		fyne.NewAnimation(myTheme.AnimationDurationShort, func(f float32) {
 			w := (200-minW)*f + minW
 			searchEntry.SetMinWidth(w)

ui/widgets/auxcontrols.go

@@ -124,7 +124,9 @@ func NewVolumeSlider(width float32) *volumeSlider {
 
 func (v *volumeSlider) Tapped(e *fyne.PointEvent) {
 	v.Slider.Tapped(e)
-	fyne.CurrentApp().Driver().CanvasForObject(v).Unfocus()
+	if c := fyne.CurrentApp().Driver().CanvasForObject(v); c != nil {
+		c.Unfocus()
+	}
 }
 
 func (v *volumeSlider) MinSize() fyne.Size {

ui/widgets/focuslist.go

@@ -67,7 +67,9 @@ func (g *FocusList) FocusNeighbor(curItem widget.ListItemID, up bool) {
 	other := g.ItemForID(focusIdx)
 	g.mutex.Unlock()
 	if other != nil {
-		fyne.CurrentApp().Driver().CanvasForObject(g).Focus(other.(fyne.Focusable))
+		if c := fyne.CurrentApp().Driver().CanvasForObject(g); c != nil {
+			c.Focus(other.(fyne.Focusable))
+		}
 	}
 }
 
@@ -120,8 +122,7 @@ func (l *FocusListRowBase) SetItemID(id widget.ListItemID) {
 
 func (l *FocusListRowBase) EnsureUnfocused() {
 	if l.Focused {
-		c := fyne.CurrentApp().Driver().CanvasForObject(l)
-		if c != nil {
+		if c := fyne.CurrentApp().Driver().CanvasForObject(l); c != nil {
 			c.Unfocus()
 		}
 	}

ui/widgets/gridview.go

@@ -286,7 +286,9 @@ func (g *GridView) Resize(size fyne.Size) {
 var _ fyne.Tappable = (*GridView)(nil)
 
 func (g *GridView) Tapped(*fyne.PointEvent) {
-	fyne.CurrentApp().Driver().CanvasForObject(g).Unfocus()
+	if c := fyne.CurrentApp().Driver().CanvasForObject(g); c != nil {
+		c.Unfocus()
+	}
 }
 
 func (g *GridView) createGridWrap() {
@@ -343,7 +345,9 @@ func (g *GridView) createNewItemCard() fyne.CanvasObject {
 			g.grid.ScrollTo(focusIndex)
 			g.stateMutex.RLock()
 			if item, ok := g.itemForIndex[focusIndex]; ok {
-				fyne.CurrentApp().Driver().CanvasForObject(g).Focus(item)
+				if c := fyne.CurrentApp().Driver().CanvasForObject(g); c != nil {
+					c.Focus(item)
+				}
 			}
 			g.stateMutex.RUnlock()
 		}

ui/widgets/gridviewitem.go

@@ -513,8 +513,10 @@ func (g *GridViewItem) Update(model *GridViewItemModel) {
 	g.secondaryText.Refresh()
 	g.Cover.ResetPlayButton()
 	if g.focused {
-		fyne.CurrentApp().Driver().CanvasForObject(g).Focus(nil)
-		g.FocusLost()
+		if c := fyne.CurrentApp().Driver().CanvasForObject(g); c != nil {
+			c.Unfocus()
+			g.FocusLost()
+		}
 	}
 }
 
@@ -589,7 +591,9 @@ func (g *GridViewItem) TypedRune(rune) {
 var _ fyne.Tappable = (*GridViewItem)(nil)
 
 func (g *GridViewItem) Tapped(*fyne.PointEvent) {
-	fyne.CurrentApp().Driver().CanvasForObject(g).Unfocus()
+	if c := fyne.CurrentApp().Driver().CanvasForObject(g); c != nil {
+		c.Unfocus()
+	}
 }
 
 func (g *GridViewItem) CreateRenderer() fyne.WidgetRenderer {

ui/widgets/playercontrols.go

@@ -50,7 +50,9 @@ func (t *TrackPosSlider) Tapped(e *fyne.PointEvent) {
 	t.Slider.Tapped(e)
 
 	// don't keep focus after being tapped
-	fyne.CurrentApp().Driver().CanvasForObject(t).Focus(nil)
+	if c := fyne.CurrentApp().Driver().CanvasForObject(t); c != nil {
+		c.Unfocus()
+	}
 }
 
 // override to increase the distance moved by keyboard control

ui/widgets/searchentry.go

@@ -50,7 +50,9 @@ func (sf *SearchEntry) Init() {
 func (s *SearchEntry) TypedKey(e *fyne.KeyEvent) {
 	if e.Name == fyne.KeyEscape {
 		s.SetText("")
-		fyne.CurrentApp().Driver().CanvasForObject(s).Unfocus()
+		if c := fyne.CurrentApp().Driver().CanvasForObject(s); c != nil {
+			c.Unfocus()
+		}
 		return
 	}
 	s.Entry.TypedKey(e)