Merge branch 'master' into ft/oas3

src/core/components/providers/markdown.jsx

@@ -1,9 +1,16 @@
-import React, { PropTypes } from "react"
+import React from "react"
+import PropTypes from "prop-types"
 import Remarkable from "react-remarkable"
 import sanitize from "sanitize-html"
 
 function Markdown({ source }) {
   const sanitized = sanitizer(source)
+
+  // sometimes the sanitizer returns "undefined" as a string
+  if(!source || !sanitized || sanitized === "undefined") {
+    return null
+  }
+
   return <Remarkable
     options={{html: true, typographer: true, linkify: true, linkTarget: "_blank"}}
     source={sanitized}