fixed issue #48 Table filtering broken by var that=this

nginx/covid_website/assets/js/trials-map.js

@@ -425,9 +425,11 @@ class TrialsMap {
     // Apply the search
     table.columns().every(function () {
       $('input', this.footer()).on('keyup change clear', () => {
+        var that = this
+        var searchPhrase = that.footer().lastChild.value
         console.log("event")
-        if (this.search() !== this.value) {
-          this.search(this.value).draw()
+        if (that.search() !== searchPhrase) {
+          that.search(searchPhrase).draw()
         }
       })
     })