Specify defaultcase for dashboard address

Iff the dashboard should listen to all interfaces this should be expressed here since empty strings should respect the given host argument

distributed/node.py

@@ -143,8 +143,13 @@ def start_http_server(
         self.http_server = HTTPServer(self.http_application, ssl_options=ssl_options)
 
         http_addresses = clean_dashboard_address(dashboard_address or default_port)
-
         for http_address in http_addresses:
+            # Handle default case for dashboard address
+            # In case dashboard_address is given, e.g. ":8787"
+            # the address is empty and it is intended to listen to all interfaces
+            if dashboard_address is not None and http_address["address"] == "":
+                http_address["address"] = "0.0.0.0"
+
             if http_address["address"] is None or http_address["address"] == "":
                 address = self._start_address
                 if isinstance(address, (list, tuple)):