Properly initialize displaysize

Properly initialize displaysize

From Microsoft's `SQLColAttribute()` documentation[1]:

| Please note that some drivers may only write the lower 32-bit or
| 16-bit of a buffer and leave the higher-order bit unchanged.
| Therefore, applications should initialize the value to 0 before
| calling this function.

[1] <https://docs.microsoft.com/en-us/sql/odbc/reference/syntax/sqlcolattribute-function>