fixed settings manager where no camera is connected

didn't check yet

backend/app/classes/Exceptions.py

@@ -3,3 +3,9 @@ class PipelineAlreadyExistsException(Exception):
 
     def __init__(self, pipe_name):
         super(f"Pipeline {pipe_name} already exists")
+
+
+class NoCameraConnectedException(Exception):
+
+    def __init__(self):
+        super("No camera as been detected")