WARNING: 51499 : Use of uninitialized value in subtraction (-)

[DadongZ]

I got many warnings from converting my mutect2's output vcf to maf such like

WARNING: 51420 : Use of uninitialized value in subtraction (-) at /home.local/dz33/ensembl-vep/modules/Bio/EnsEMBL/VEP/AnnotationSource/Cache/VariationTabix.pm line 184, <VARS> line 1.
Use of uninitialized value in addition (+) at /home.local/dz33/ensembl-vep/modules/Bio/EnsEMBL/VEP/AnnotationSource/Cache/VariationTabix.pm line 184, <VARS> line 1.
WARNING: 51418 : Use of uninitialized value in subtraction (-) at /home.local/dz33/ensembl-vep/modules/Bio/EnsEMBL/VEP/AnnotationSource/Cache/VariationTabix.pm line 184, <VARS> line 1.
Use of uninitialized value in addition (+) at /home.local/dz33/ensembl-vep/modules/Bio/EnsEMBL/VEP/AnnotationSource/Cache/VariationTabix.pm line 184, <VARS> line 1.
WARNING: 51414 : Use of uninitialized value in subtraction (-) at /home.local/dz33/ensembl-vep/modules/Bio/EnsEMBL/VEP/AnnotationSource/Cache/VariationTabix.pm line 184, <VARS> line 1.
Use of uninitialized value in addition (+) at /home.local/dz33/ensembl-vep/modules/Bio/EnsEMBL/VEP/AnnotationSource/Cache/VariationTabix.pm line 184, <VARS> line 1.

What are the concerns behind them?

[JLiandbear]

See same warning here. Wondering whether it's a real concern or harmless?