FilterExec should not return Non Statistics when it can not calculate the predicate selectivity

**Describe the bug**
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https://github.com/apache/arrow-datafusion/blob/58b43f5c0b629be49a3efa0e37052ec51d9ba3fe/datafusion/core/src/physical_plan/filter.rs#L173-L193

Should return `input_stats`

**To Reproduce**
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**Expected behavior**
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**Additional context**
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Start in datafusion/core/src/physical_plan/filter.rs at lines 173-193 and inspect how FilterExec handles predicate selectivity. Verify the behavior when selectivity cannot be calculated, then confirm that the result preserves input statistics as described. The issue does not name a reproduction or test file, so identify the relevant existing statistics tests before making the change.

Written by the indexing model from the issue text.