fix: empty initial value in parameter calc mode

...-param-computed/dialog-edit-param-computed.component.html

...it-param-computed/dialog-edit-param-computed.component.ts

src/app/components/ngparam-input/ngparam-input.component.ts

...app/components/param-computed/param-computed.component.ts

...components/param-field-line/param-field-line.component.ts

src/app/formulaire/elements/ngparam.ts