fix(span): fallback to client environment if not provided (#1304)

Author: Digma

langfuse/_client/span.py

@@ -123,7 +123,7 @@ def __init__(
         self.trace_id = self._langfuse_client._get_otel_trace_id(otel_span)
         self.id = self._langfuse_client._get_otel_span_id(otel_span)
 
-        self._environment = environment
+        self._environment = environment or self._langfuse_client._environment
         if self._environment is not None:
             self._otel_span.set_attribute(
                 LangfuseOtelSpanAttributes.ENVIRONMENT, self._environment