Perl error in pg_dump_backup service

[ioguix]

The pg_dump_backup is sometime failing with some perl warning.

Use of uninitialized value in subtraction (-) at ./bin/check_pgactivity line 6594.
Use of uninitialized value $ratio in multiplication (*) at ./bin/check_pgactivity line 873.
Use of uninitialized value $ratio in multiplication (*) at ./bin/check_pgactivity line 873.
Use of uninitialized value in subtraction (-) at ./bin/check_pgactivity line 6642.
POSTGRES_PGDUMP_BACKUP CRITICAL: 'db1_delta'=120062394B, 'db2_oldest'=NaNs, 'db2_newest'=NaNs, 'db2_size'=NaNB, 'db3_oldest'=NaNs, 'db3_newest'=NaNs, 'db3_size'=NaNB, 'db4_oldest'=NaNs, 'db4_newest'=NaNs, 'db4_size'=NaNB, 'db4_oldest'=NaNs, 'db5_newest'=NaNs, 'db5_size'=NaNB, 'db5_newest'=1d 16m17s

We do not know exactly how to reproduce this issue. This might comes from an empty status file, maybe from a new database appearing between two checks or anything else...