Searching with an empty query

[AyahSoufan]

Describe the bug
When searching with an empty query in the query box the home page is opened with the default query (Natural Language processing)

To Reproduce
Steps to reproduce the behavior:

1. Open the system, search for anything you want. (ex, Natural Language processing).
2. When the results are shown, clear the search box.
3. Click search
4. Notice that you were directed to the home page with the default query.

Expected behavior
The searcher should stay on the same page and a clear message should be shown for the searcher says "Please enter a query in the search box above."