Fix: new doc route is invalid when partition is selected (#1182)

diff --git a/app/addons/documents/routes-doc-editor.js b/app/addons/documents/routes-doc-editor.js
index 6a54796..f0d8e7e 100644
--- a/app/addons/documents/routes-doc-editor.js
+++ b/app/addons/documents/routes-doc-editor.js
@@ -41,8 +41,8 @@
     'database/:database/_design/:ddoc': 'showDesignDoc',
     'database/:database/_local/:doc': 'showLocalDoc',
     'database/:database/:doc': 'codeEditor',
-    'database/:database/_new': 'codeEditor',
-    'database/:database/_new?(:extra)': 'codeEditor'
+    'database/:database/_new': 'codeEditorNewDoc',
+    'database/:database/_new?(:extra)': 'codeEditorNewDoc'
   },
 
   revisionBrowser: function (databaseName, docId) {
@@ -66,6 +66,10 @@
     return this.revisionBrowser(databaseName, '_design/' + ddoc);
   },
 
+  codeEditorNewDoc: function (databaseName, options) {
+    return this.codeEditor(databaseName, null, options);
+  },
+
   codeEditor: function (databaseName, docId, options) {
     const urlParams = app.getParams(options);
     const backLink = FauxtonAPI.urls('allDocs', 'app', FauxtonAPI.url.encode(databaseName));