TableOutputComponent: Fix backward search upon index 0

Before this change, a backward search while selecting the first entry in
a table (index 0) would unselect it while trying to reach index -1.

Preserve such a selection instead, making the potential backward search
(user action) a no-op.

Contributes to fixing #859.

Signed-off-by: Marco Miller <marco.miller@ericsson.com>

packages/react-components/src/components/table-output-component.tsx

@@ -641,6 +641,10 @@ export class TableOutputComponent extends AbstractOutputComponent<TableOutputPro
                     currRowIndex = Math.max(this.selectStartIndex, this.selectEndIndex) + 1;
                 } else {
                     currRowIndex = Math.min(this.selectStartIndex, this.selectEndIndex) - 1;
+                    if (currRowIndex < 0) {
+                        // no backward search if already at index 0
+                        return;
+                    }
                 }
             } else if (direction === Direction.PREVIOUS) {
                 // no backward search if there is no selection