Fix binding merging a la #1336

Author: rodrigogiraoserrao

src/textual/dom.py

@@ -229,7 +229,7 @@ def _merge_bindings(cls) -> Bindings:
             if issubclass(base, DOMNode):
                 if not base._inherit_bindings:
                     bindings.clear()
-                bindings.append(Bindings(base.BINDINGS))
+                bindings.append(Bindings(base.__dict__.get("BINDINGS", [])))
         keys = {}
         for bindings_ in bindings:
             keys.update(bindings_.keys)