views: Warn user when no logs available

Warn user if trying to access the logs of a client that don't yet exist.
This is prefered to showing the backtrace to the user.

ogcp/views.py

@@ -2100,6 +2100,9 @@ def action_legacy_log():
         return redirect(url_for('commands'))
     ip = ips.pop()
     log_file = Path("/opt/opengnsys/log/clients/" + str(ip) + ".log")
+    if not os.access(log_file, os.R_OK):
+        flash(_('No log available for this client yet'), category='error')
+        return redirect(url_for('commands'))
     log = log_file.read_text()
     if log:
         scopes, clients = get_scopes(set(ips))