[Bug] 'Planned' | issue with 'Worked time' input logic

[KostyaEver]

The issue is that when there is a default value '0' in the input and the user clicks into the input with the mouse the value '0' is still there. and if the user does not erase the value, the next added value will be added as the next '0 + X'

Expect:

1. When there is '0' value and the user clicks into the input, it should erase automatically '0' so that user can pup any preferable value, but if the user did not put, the system should take back '0' value

2. Another issue, that should not be allowed format '0 -X' adding values after '0', it may confuse the user

Should be only like here