Validate calculation for month without an individual shift

[WalBeh]

Issue

Recently I noticed that at the report summary, the calculation needs to be verified again,
for cases where there is not 24x7 for an member in the whole month. To make sure the
calculation over the "re-balanced time-window" is correct.

For example:

xx@expamle.io                  2024 Jul   16.0         88.96           510.00          0.00
xx@example.io                  2024 Aug   0.3          1.61            510.00          0.00
xx@example.io                  2024 Oct   114.0        633.84          510.00          123.84
xx@example.io                  2024 Dec   102.0        567.12          510.00          57.12
                               SUBTOTAL   232.3        1291.53         2040.00         0.00

November is missing here. In this case it does not make a difference at all.

Expected behaviour

In such a case "November" needs to be reported as "0" and the monthly pre-payment has to be
considered.

xx@expamle.io                  2024 Jul   16.0         88.96           510.00          0.00
xx@example.io                  2024 Aug   0.3          1.61            510.00          0.00
xx@example.io                  2024 Oct   114.0        633.84          510.00          123.84
xx@example.io                  2024 Nov   0.0          0.0             510.00          0.0
xx@example.io                  2024 Dec   102.0        567.12          510.00          57.12
                               SUBTOTAL   232.3        1291.53         2550.00         0.00

[amotl]

Hi. I think this has been fixed with GH-3 already? Let's run a release to make it available?