Fixed issue re-selection selected groups when exiting search.

This fix is rather ugly but works for now. It should get re-evaluated when the whole selection and search model is being refactored

MacPass/MPDocument+Search.m

@@ -49,6 +49,9 @@ NSString *const kMPDocumentSearchResultsKey           = @"kMPDocumentSearchResul
    */
   [NSNotificationCenter.defaultCenter postNotificationName:MPDocumentDidEnterSearchNotification object:self];
   [self updateSearch:self];
+  /* clear selection */
+  self.selectedGroups = nil;
+  self.selectedEntries = nil;
 }
 
 #pragma mark Actions