Panic in ParquetMetadata::memory_size if no min/max set

[Ma1oneZhang]

Describe the bug

In the 52.1.0 release of the parquet crate, new APIs were introduced to retrieve the heap size of parquet metadata. However, a potential issue has been identified in the implementation that could lead to unexpected panics. The problem lies in the file 'parquet/src/file/meta/memory.rs', specifically between lines 168-178. In this section, the code invokes the 'min' function without first verifying the presence of a value in an Option type. This lack of validation before unwrapping could result in a panic if the Option is None.

To Reproduce

Construct a ValueStatistics without min/max value, and invoke the heapsize function.

Expected behavior

return current heap_size

Additional context
NONE

[Ma1oneZhang]

@alamb Please check the issue