Fix insufficient slice check (#2755)

tree_test.go

@@ -717,6 +717,19 @@ func TestTreeInvalidNodeType(t *testing.T) {
 	}
 }
 
+func TestTreeInvalidParamsType(t *testing.T) {
+	tree := &node{}
+	tree.wildChild = true
+	tree.children = append(tree.children, &node{})
+	tree.children[0].nType = 2
+
+	// set invalid Params type
+	params := make(Params, 0, 0)
+
+	// try to trigger slice bounds out of range with capacity 0
+	tree.getValue("/test", &params, false)
+}
+
 func TestTreeWildcardConflictEx(t *testing.T) {
 	conflicts := [...]struct {
 		route        string