tui/layout.go: fix crash

1 files changed, 15 insertions, 11 deletions

diff --git a/tui/layout.go b/tui/layout.go
index 398c0b1..9acc65b 100644
--- a/tui/layout.go
+++ b/tui/layout.go
@@ -277,19 +277,23 @@ func (b *Box) computePositions(axis int) {
 			}
 		}
 		if b.Scroll != nil {
-			first := b.children[0]
-			last := b.children[len(b.children) - 1]
+			var first, last *Box
+			if len(b.children) > 0 {
+				first = b.children[0]
+				last = b.children[len(b.children) - 1]
+			}
 
-			lastPos := last.computedPosition
-			lastPos += last.computedSize[axis]
-			if b.Dir.reverse() {
-				lastPos = b.computedSize[axis] - lastPos
+			if last != nil {
+				lastPos := last.computedPosition
+				lastPos += last.computedSize[axis]
+				if b.Dir.reverse() {
+					lastPos = b.computedSize[axis] - lastPos
+				}
+				b.Scroll.absolute = min(b.Scroll.absolute, lastPos - b.computedSize[axis])
 			}
-			b.Scroll.absolute = min(b.Scroll.absolute, lastPos - b.computedSize[axis])
 			b.Scroll.absolute = max(b.Scroll.absolute, 0)
 
-			var firstShown *Box
-			var lastShown *Box
+			var firstShown, lastShown *Box
 			for _, c := range b.children {
 				if !b.Dir.reverse() {
 					c.computedPosition -= b.Scroll.absolute
@@ -299,9 +303,9 @@ func (b *Box) computePositions(axis int) {
 				if c.computedPosition > b.computedRect.min[axis] &&
 						c.computedPosition < b.computedRect.max[axis] {
 					if firstShown == nil {
-						first = c
+						firstShown = c
 					}
-					last = c
+					lastShown = c
 				}
 			}
 			if firstShown == first {