js: add check to eliminate js errors when inline comment function references an object which does not exist

rhodecode/public/js/src/rhodecode/comments.js

@@ -282,8 +282,10 b' var placeInline = function(target_contai'
   var target_line = $('#' + lineid).get(0);
   var comment = new $(tableTr('inline-comments', html));
   // check if there are comments already !
+  if (target_line) {
   var parent_node = target_line.parentNode;
   var root_parent = parent_node;
+
   while (1) {
     var n = parent_node.nextElementSibling;
     // next element are comments !
@@ -301,6 +303,7 b' var placeInline = function(target_contai'
   if (show_add_button) {
     placeAddButton(root_parent);
   }
+  }
 
   return target_line;
 };