Fix ansispan() to ignore stray [0m

IPython/html/static/base/js/utils.js

@@ -284,11 +284,19 b' define(['
     function ansispan(str) {
         // ansispan function adapted from github.com/mmalecki/ansispan (MIT License)
         // regular ansi escapes (using the table above)
+        var is_open = false
         return str.replace(/\033\[(0?[01]|22|39)?([;\d]+)?m/g, function(match, prefix, pattern) {
             if (!pattern) {
                 // [(01|22|39|)m close spans
+                if (is_open) {
+                    is_open = false;
                 return "</span>";
+                } else {
+                    return "";
             }
+            } else {
+                is_open = true;
+
             // consume sequence of color escapes
             var numbers = pattern.match(/\d+/g);
             var attrs = {};
@@ -302,6 +310,7 b' define(['
                 span = span + " " + attr + '="' + attrs[attr] + '"';
             }
             return span + ">";
+            }
         });
     };