fix(avl): add missing checks in avl package

examples/gno.land/p/nt/avl/node.gno

@@ -108,12 +108,15 @@ func (node *Node) Get(key string) (index int, value any, exists bool) {
 // GetByIndex retrieves the key-value pair of the node at the given index
 // in the subtree rooted at the node.
 func (node *Node) GetByIndex(index int) (key string, value any) {
+	if index < 0 {
+		panic("GetByIndex: negative index not allowed")
+	}
+
 	if node.height == 0 {
-		if index == 0 {
-			return node.key, node.value
-		} else {
+		if index != 0 {
 			panic("GetByIndex asked for invalid index")
 		}
+		return node.key, node.value
 	} else {
 		// TODO: could improve this by storing the sizes
 		leftNode := node.getLeftNode()
@@ -267,6 +270,13 @@ func (node *Node) rotateLeft() *Node {
 func (node *Node) calcHeightAndSize() {
 	node.height = maxInt8(node.getLeftNode().height, node.getRightNode().height) + 1
 	node.size = node.getLeftNode().size + node.getRightNode().size
+
+	if node.height < 0 {
+		panic("height overflow: tree height exceeds int8 max")
+	}
+	if node.size < 0 {
+		panic("size overflow: node size exceeds int max")
+	}
 }
 
 // calcBalance calculates the balance factor of the node.

examples/gno.land/p/nt/avl/pager/pager.gno

@@ -53,6 +53,10 @@ func (p *Pager) GetPage(pageNumber int) *Page {
 }
 
 func (p *Pager) GetPageWithSize(pageNumber, pageSize int) *Page {
+	if pageSize <= 0 {
+		panic("GetPageWithSize: invalid page size")
+	}
+
 	totalItems := p.Tree.Size()
 	totalPages := int(math.Ceil(float64(totalItems) / float64(pageSize)))