FIX: Return an empty lxml.Element as metadata for S1 RTC ASF products instead of None to ensure consistency

Author: remi-braun

CHANGES.md

@@ -24,6 +24,7 @@
 - FIX: Handle GCPs in VHR data
 - FIX: Fix raw CRS exported as string rather than CRS object for Maxar data [#255](https://github.com/sertit/eoreader/issues/255)
 - FIX: Use only the number of range looks to derive the resolution and pixel_size of CSG data [#256](https://github.com/sertit/eoreader/issues/256)
+- FIX: Retunr an empty `lxml.Element` as metadata for S1 RTC ASF products instead of `None` to ensure consistency
 - OPTIM: Use raw band path over default band path to speed up the computation of image information (extent, footprint, CRS, transform) of SAR ortho products
 - OPTIM: Allow predictor = 3 with LZW compression when saving SAR intermediate data as SNAP handles it properly now. [#173](https://github.com/sertit/eoreader/issues/173)
 - CI: Filter some warnings in pytest

eoreader/products/sar/s1_rtc_asf_product.py

@@ -271,7 +271,7 @@ def _read_mtd(self) -> (etree._Element, dict):
             (etree._Element, dict): Metadata XML root and its namespaces
         """
         # No MTD!
-        return None, {}
+        return etree.Element("root"), {}
 
     def get_quicklook_path(self) -> str:
         """