private static @Nullable String findPrevFile(@NotNull JTable table, int row, int column) {
        if (row <= 0) return null;
        Object prev = table.getValueAt(row - 1, column);
        if (!(prev instanceof FindPopupItem)) {
          return null;
        }
        UsagePresentation presentation = ((FindPopupItem)prev).getPresentation();
        if (presentation == null) {
          return null;
        }
        return presentation.getFileString();
      }
private static @Nullable String findPrevFile(@NotNull JTable table, int row, int column)