fix solvers

Author: cedricvincentcuaz

ot/solvers.py

@@ -1040,9 +1040,17 @@ def solve_gromov(
                 # potentials = (log['u'], log['v']) TODO
 
             else:  # partial FGW
-                if unbalanced > nx.sum(a) or unbalanced > nx.sum(b):
-                    raise (ValueError("Partial FGW mass given in reg is too large"))
+                if unbalanced is None:
+                    raise (
+                        ValueError(
+                            "Partial GW mass given in `unbalanced` must be float and not None"
+                        )
+                    )
 
+                elif unbalanced > nx.sum(a) or unbalanced > nx.sum(b):
+                    raise (
+                        ValueError("Partial GW mass given in `unbalanced` is too large")
+                    )
                 # default values for solver
                 if max_iter is None:
                     max_iter = 1000