Don't check for IDA Pro if it is dissabled (#439)

pwndbg/ida.py

@@ -88,6 +88,8 @@ class withIDA(object):
         functools.update_wrapper(self, fn)
 
     def __call__(self, *args, **kwargs):
+        if not ida_enabled:
+            return None
         if _ida is None:
             init_ida_rpc_client()
         if _ida is not None: