Previously the slider scrolled on every keypress

Replaces getPDO()->exec() with execSQL()

There where syntax errors in the SQL statement.
Furthermore the primary keys are only dropped if they exist.
This prevents unnecessary errors/messages in the logs.

Co-authored-by: Adrian Müller <adrian@pcsg.de>

#117

The value of the attribute isMobileSlidesEnabled is "0" or "1" (as a string) with the previous === check this always evaluated to false.