Ungauged nodes: crash with a reservoir and several upstrem nodes

The calibration crashes with a reservoir with 2 upstream nodes with at least one ungauged:

graph LR

id_54001[54001]
id_54029[54029]
id_54032[54032]

id_Dam[Dam]

id_54001 -->| 45 km| id_Dam
id_54029 -->| 32 km| id_Dam

id_Dam -->| 0 km| id_54032

class id_54001 UpstreamUngauged
class id_54029 UpstreamGauged
class id_54032 IntermediateGauged

class id_Dam Reservoir

classDef default stroke:#333

classDef UpstreamUngauged fill:#eef

classDef UpstreamGauged fill:#aaf

classDef IntermediateUngauged fill:#efe

classDef IntermediateGauged fill:#afa

classDef DirectInjection fill:#faa

classDef Reservoir fill:#9de

classDef UpstreamUngaugedDiversion fill:#eef, stroke:#faa, stroke-width:3px

classDef UpstreamGaugedDiversion fill:#aaf, stroke:#faa, stroke-width:3px

classDef IntermediateUngaugedDiversion fill:#efe, stroke:#faa, stroke-width:3px

classDef IntermediateGaugedDiversion fill:#afa, stroke:#faa, stroke-width:3px