quote data attributes

prevents errors when these are empty strings

IPython/html/templates/notebook.html

@@ -21,11 +21,11 b' window.mathjax_url = "{{mathjax_url}}";'
 
 {% block params %}
 
-data-project={{project}}
-data-base-project-url={{base_project_url}}
-data-base-kernel-url={{base_kernel_url}}
-data-notebook-name={{notebook_name}}
-data-notebook-path={{notebook_path}}
+data-project="{{project}}"
+data-base-project-url="{{base_project_url}}"
+data-base-kernel-url="{{base_kernel_url}}"
+data-notebook-name="{{notebook_name}}"
+data-notebook-path="{{notebook_path}}"
 class="notebook_app"
 
 {% endblock %}

IPython/html/templates/tree.html

@@ -10,10 +10,10 b''
 
 {% block params %}
 
-data-project={{project}}
-data-base-project-url={{base_project_url}}
-data-notebook-path={{notebook_path}}
-data-base-kernel-url={{base_kernel_url}}
+data-project="{{project}}"
+data-base-project-url="{{base_project_url}}"
+data-notebook-path="{{notebook_path}}"
+data-base-kernel-url="{{base_kernel_url}}"
 
 {% endblock %}