Problem description: Administration => General => Modules view: if the checkbox, next to a module that was removed from the modules directory, was selected, and then the "Scan directory" button is pressed, the module itself is removed from the modules list, but the count of selected modules still takes it into account.

Steps to reproduce:

1. Create at least 1 module and place it in frontends/php/modules directory.
2. Navigate to Administration => General => Modules directory and press "Scan directory" button - the created module appeard in the list of available modules.
3. Select the checkbox next to the created module.
4. Remove the module from frontends/php/modules/ directory
5. Click on the "Scan directory" button
   Result 1: there are no modules in the list, but the string in the bottom left corner of the table states "1 selected"
6. Place the created module back in the frontends/php/modules directory
7. Click on the "Scan directory" button - the created module appeared in the list of available modules once again.
8. Select the checkbox next to the created module.
   Result 2: There is only 1 module in the list, but the string in the bottom left corner of the table states "2 selected".

Expected: Modules that are not in the list should not be considered in the total number of selected modules.

Example: