Fix JSONDecodeError on sent request with no Category selected

error: json.decoder.JSONDecodeError
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

* Also add blacklist flag to url only if selected any

Signed-off-by: Hemant Sachdeva <hemant.evolver@gmail.com>

src/main.py

@@ -28,11 +28,15 @@
 def index():
     if request.method == 'POST':
         cat = request.form.getlist('catagory')
-        cat = ','.join(cat)  # making cat list a ',' separated string
+        if cat:
+            cat = ','.join(cat)  # making cat list a ',' separated string
+            url = "https://v2.jokeapi.dev/joke/{}".format(cat)
+        else:
+            url = "https://v2.jokeapi.dev/joke/Any"
         flag = request.form.getlist('flag')
-        flag = ','.join(flag)  # making flag list a ',' separated string
-        url = "https://v2.jokeapi.dev/joke/{}?blacklistFlags={}".format(
-            cat, flag)
+        if flag:
+            flag = ','.join(flag)  # making flag list a ',' separated string
+            url += '?blacklistFlags={}'.format(flag)
         resp = requests.get(url)
         data = resp.json()
         if data.get('type') == 'single':