Describe the bug
Item creation fails for Collection 2 Level-1 data when a NULL value is encountered in the MTL xml metadata for "add" and "mult" values (used to convert from DN to radiance).
To reproduce
Create a STAC Item from a scene with NULL values indicated above, e.g., LM01_L1GS_007019_19771009_20200907_02_T2
Describe the bug Item creation fails for Collection 2 Level-1 data when a NULL value is encountered in the MTL xml metadata for "add" and "mult" values (used to convert from DN to radiance).
To reproduce Create a STAC Item from a scene with NULL values indicated above, e.g., LM01_L1GS_007019_19771009_20200907_02_T2
Expected behavior Item creation should not fail.