Commented Unassigned: Using SUMIF results in a "Syntax error." exception [9442]

Using

```
SUMIF(A1:A10,">0")
```

results in a "Syntax error." exception.


Code ends up in the ParseAtom() method with the _token.Type of TKTYPE.COMPARE, which is unsupported at that moment.
Comments: The fix is to just replace the value with 0 if it's blank in the built expression. MathTrig.cs line 258