Bug in Filtering Custom Fields

Hi Franky,

I found a bug when using the filter form with two (or more) custom fields:

1. Have two checkbox custom fields, with options X1,X2 and Y1,Y2
2. Create a page with the filter form: [eme_filterform][eme_events]
3. Filter for X1 and Y1

If none of my events have X1, then the form correctly returns no results. However, if even just one event contains X1, the results I get are all the events with Y1, whether they contain X1 or not. It seems the filter is ignoring my X selection in this case.

Again big thanks for putting your time into this plugin. It helped my church organise our attendance during this COVID period.