In cells with formulas containing conditions like `=IFSUM(A1:A3;"";B1:B3)`
to sum cells from range A1:A3 with empty value in range B1:B3, the function
`Functions::ifCondition()` create in this case the code `=""""` instead of
`=""`, so it didn't work.
Closes#1206
Conditional operators in the selection parameter of COUNTIF
functions were not being parsed properly, causing evaluations
of formulae with such functions to sometimes fail.
Fixes#526Closes#528
