Legacy GUI & binding constraint of type "both"

[guilpier-code]

Description of the bug :
When creating BC of type"both" with legacy GUI, saving this change causes a misleading error message : "Cannot load time series of type other that eq/gt/lt". Note that it does not occur with any other binding constraint type : greater, less, equal.

Context : Remind that, since GUI v8.7, whatever the type of BC (binding constraint) we want to create, we cannot we create a whole BC with the GUI : we can create the BC, but, within the BC, giving coefficients to link flows or thermal productions is impossible, as well as setting RHS values.

How to reproduce :

• Create an empty study with one area.
• Add a BC of type both
• Without trying to give values to LHS assets or to RHS, save the study
• The error message pops up

Version :

• GUI v8.7
• System : at least on Win