When any of the docked tab(statistics, dependents & dependencies)

are clicked without selecting any tree node. it gives error in browser
console panel.
Because the node passed is undefined. and check is missing. This is now
fixed by adding check for node passed.

web/pgadmin/misc/statistics/static/js/statistics.js

@@ -218,6 +218,9 @@ function(_, $, pgBrowser, Backgrid) {
 
     showStatistics: function(item, data, node) {
       var self = this;
+      if (!node) {
+        return;
+      }
       /**
        * We can't start fetching the statistics immediately, it is possible -
        * the user is just using keyboards to select the node, and just