Fixes #11553: Prevent double border on tables in panels without thead content

dist/css/bootstrap.css

@@ -5585,6 +5585,11 @@ a.list-group-item.active:focus .list-group-item-text {
   border-top: 1px solid #dddddd;
 }
 
+.panel > .table > tbody:first-child th,
+.panel > .table > tbody:first-child td {
+  border-top: 0;
+}
+
 .panel > .table-bordered,
 .panel > .table-responsive > .table-bordered {
   border: 0;

less/panels.less

@@ -64,6 +64,10 @@
   > .panel-body + .table-responsive {
     border-top: 1px solid @table-border-color;
   }
+  > .table > tbody:first-child th,
+  > .table > tbody:first-child td {
+    border-top: 0;
+  }
   > .table-bordered,
   > .table-responsive > .table-bordered {
     border: 0;