Apache Airflow version: 1.10.10

Kubernetes version (if you are using kubernetes) (use kubectl version):

Environment:

• Cloud provider or hardware configuration:
• OS (e.g. from /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
• Others:

What happened:

If you run DAG with {""": ""} configuration tree view will be broken

What you expected to happen:

How to reproduce it:
If you run DAG with {""": ""} configuration tree view will be broken:

tree:1 Uncaught SyntaxError: Unexpected string in JSON at position 806
    at JSON.parse (<anonymous>)
    at tree?dag_id=hightlight_test&num_runs=25:1190

JSON.parse is given incorrectly escaped json string.

Anything else we need to know: