support nested formula in if formula

[bailantaotao]

Description
if i place the round formula in if formula, it will return empty string

Steps to reproduce the issue:

1. set formula to IF(TRUE, ROUND(4/2,0),0) then calculate it

Describe the results you received:
empty string

Describe the results you expected:
2

Output of go version:

1.16.6

Excelize version or commit ID:

2.4.1

Environment details (OS, Microsoft Excel™ version, physical, etc.):
MAC os 11.5