Fix add to Collection on Safari Mobile

Steps to reproduce:

• Navigate to a folder containing several documents.
• Select some of the files.
• Tap on the Add to Collection document action.
  => Collection dialog appears.
• Tap on the field and start entering the name of a new collection.
  => The automatic zoom on the dialog limits the view of the field.
  => The drop down suggestions which you have to tap on to select an existing or new collection is not in view.
  => Cursor advances without displaying the writing text.

View screencast here