Fix: Allow for selection of text before items are selected in the table

- Rather than checking for an empty selection, need to check to see if the selection has changed from mousedown to the click event
- https://datatables.net/forums/discussion/comment/127487#Comment_127487

js/dataTables.select.js

@@ -324,6 +324,7 @@ function enableMouseSelection ( dt )
 	var container = $( dt.table().container() );
 	var ctx = dt.settings()[0];
 	var selector = ctx._select.selector;
+	var matchSelection;
 
 	container
 		.on( 'mousedown.dtSelect', selector, function(e) {
@@ -336,6 +337,10 @@ function enableMouseSelection ( dt )
 						return false;
 					} );
 			}
+
+			if ( window.getSelection ) {
+				matchSelection = window.getSelection();
+			}
 		} )
 		.on( 'mouseup.dtSelect', selector, function() {
 			// Allow text selection to occur again, Mozilla style (tested in FF
@@ -354,7 +359,7 @@ function enableMouseSelection ( dt )
 				// If the element that contains the selection is not in the table, we can ignore it
 				// This can happen if the developer selects text from the click event
 				if ( ! selection.anchorNode || $(selection.anchorNode).closest('table')[0] === dt.table().node() ) {
-					if ( $.trim(selection.toString()) !== '' ) {
+					if ( selection !== matchSelection ) {
 						return;
 					}
 				}