PrimProc crash in float/double to string conversion

Steps to reproduce:

1. Create table

create table test.t1 (a double, b double) engine=columnstore;

2. Run the attached PHP script as follows:

php mcol1826.php > mcol1826.csv

3. Insert the data:

cpimport test t1 mcol1826.csv

4. Run the query:

select concat_ws(':', a, b) from t1;

PrimProc will crash most of the time (may require a ColumnStore restart and retry if it doesn't)