Python3 Json.loads value type error

**When i try to click the web.py file, it run successfully to display the index page , however, when i tried to click the allblocks url page it gives me an error saying saying:
json.loads(...) ValueError: Expecting value: line 1 column 1 (char 0)**

### ** the code for part of the file bringing the error is**
`@app.route('/allblocks')
def mined_blocks():
"""
Endpoint to list all mined blocks.
"""
with open('chain.txt', 'r') as jsonfile:
data = json.loads(jsonfile)
jsonfile.close()
return render_template('blocks.html', data=data)`