This closes #2445, fix incorrect if result when third arg is missing

[Aprax14]

PR Details

Description

Make the IF function return FALSE when the condition is false and third argument is omitted. Before this change, it returned an empty string.

Related Issue

#2445

Motivation and Context

Excel returns FALSE in expressions like =IF(1=2,1). Excelize returned an empty string instead, so the result could not be used in arithmetic expressions: IF(1=2,1,IF(1=2,1))*2 returned #VALUE! instead of 0.

How Has This Been Tested

Added unit tests

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.72%. Comparing base (1cf5392) to head (5db21b8).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2446   +/-   ##
=======================================
  Coverage   99.72%   99.72%           
=======================================
  Files          32       32           
  Lines       32527    32528    +1     
=======================================
+ Hits        32437    32438    +1     
  Misses         88       88           
  Partials        2        2           

Flag	Coverage Δ
unittests	99.72% <100.00%> (+<0.01%)	⬆️

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[xuri]

Good catch! Thanks for your contribution.