[py] Fix BrowserError issues (#12150)

* [py] Fix KeyError on BrowserError

* [py] Fix TypeError on BrowserError

---------

Co-authored-by: Diego Molina <diemol@users.noreply.github.com>

Author: bastimeyer

py/selenium/webdriver/common/bidi/cdp.py

@@ -147,8 +147,8 @@ class BrowserError(Exception):
     indicates that an error occurred."""
 
     def __init__(self, obj):
-        self.code = obj["code"]
-        self.message = obj["message"]
+        self.code = obj.get("code")
+        self.message = obj.get("message")
         self.detail = obj.get("data")
 
     def __str__(self):
@@ -442,7 +442,13 @@ async def _reader_task(self):
                 try:
                     session = self.sessions[session_id]
                 except KeyError:
-                    raise BrowserError(f"Browser sent a message for an invalid session: {session_id!r}")
+                    raise BrowserError(
+                        {
+                            "code": -32700,
+                            "message": "Browser sent a message for an invalid session",
+                            "data": f"{session_id!r}",
+                        }
+                    )
                 session._handle_data(data)
             else:
                 self._handle_data(data)