types: fix nil pointer panic on NewIntFromBigInt (#9627)

types/int.go

@@ -101,8 +101,13 @@ func NewIntFromUint64(n uint64) Int {
 	return Int{b}
 }
 
-// NewIntFromBigInt constructs Int from big.Int
+// NewIntFromBigInt constructs Int from big.Int. If the provided big.Int is nil,
+// it returns an empty instance. This function panics if the bit length is > 256.
 func NewIntFromBigInt(i *big.Int) Int {
+	if i == nil {
+		return Int{}
+	}
+
 	if i.BitLen() > maxBitLen {
 		panic("NewIntFromBigInt() out of bound")
 	}

types/int_test.go

@@ -91,6 +91,9 @@ func (s *intTestSuite) TestIntPanic() {
 	s.Require().Panics(func() { intmax.Add(sdk.OneInt()) })
 	s.Require().Panics(func() { intmin.Sub(sdk.OneInt()) })
 
+	s.Require().NotPanics(func() { sdk.NewIntFromBigInt(nil) })
+	s.Require().True(sdk.NewIntFromBigInt(nil).IsNil())
+
 	// Division-by-zero check
 	s.Require().Panics(func() { i1.Quo(sdk.NewInt(0)) })