Gracefully handle non-json responses #15

pretix_matrix_inviter/helpers.py

 import requests
+from json import JSONDecodeError
 from urllib.parse import quote as url_quote
 
 
@@ -55,7 +56,10 @@ def matrix_room_id_from_alias(server, alias):
         ),
     )
 
-    return r.json().get("room_id")
+    try:
+        return r.json().get("room_id")
+    except JSONDecodeError:
+        return ""
 
 
 def matrix_room_canonical_alias_from_id(server, token, room_id):
@@ -72,7 +76,10 @@ def matrix_room_canonical_alias_from_id(server, token, room_id):
         },
     )
 
-    return r.json().get("alias")
+    try:
+        return r.json().get("alias")
+    except JSONDecodeError:
+        return ""
 
 
 def matrix_room_name_from_id(server, token, room_id):
@@ -89,4 +96,7 @@ def matrix_room_name_from_id(server, token, room_id):
         },
     )
 
-    return r.json().get("name")
+    try:
+        return r.json().get("name")
+    except JSONDecodeError:
+        return ""