UI: Fix scrollbar always present on page body (#6177)

public/less/_base.less

@@ -1,7 +1,7 @@
 body {
     font-family: "Lato", "Segoe UI", "Microsoft YaHei", Arial, Helvetica, sans-serif !important;
     background-color: #fff;
-    overflow-y: scroll;
+    overflow-y: auto;
     -webkit-font-smoothing: antialiased;
     display: flex;
     flex-direction: column;
@@ -442,7 +442,7 @@ footer {
     background-color: white;
     border-top: 1px solid #d6d6d6;
     width: 100%;
-    height: 40px;
+    flex-basis: 40px;
     color: #888888;
     .container {
         width: 100vw !important;