[Bug pyserial:172] applySettingsDict() throws an error if the settings dictionary is not complete
diff --git a/serial/serialutil.py b/serial/serialutil.py
index 0790d7d..1bd0f0c 100644
--- a/serial/serialutil.py
+++ b/serial/serialutil.py
@@ -347,7 +347,7 @@
         values will simply left unchanged.
         """
         for key in self._SETTINGS:
-            if d[key] != getattr(self, '_'+key):   # check against internal "_" value
+            if key in d and d[key] != getattr(self, '_'+key):   # check against internal "_" value
                 setattr(self, key, d[key])          # set non "_" value to use properties write function
 
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