BUG: use np.ravel avoid to run out of vars range

Author: Zeroto521

src/pyscipopt/scip.pxi

@@ -2468,17 +2468,15 @@ cdef class _VarArray:
 
     def __cinit__(self, object vars):
         if isinstance(vars, Variable):
-            self.size = 1
             vars = [vars]
-        elif isinstance(vars, (list, tuple)):
-            self.size = len(vars)
-        elif isinstance(vars, MatrixVariable):
-            self.size = vars.size
+        elif isinstance(vars, (list, tuple, MatrixVariable)):
+            vars = np.ravel(vars)
         else:
             raise TypeError(f"Expected Variable or list of Variable, got {type(vars)}.")
 
+        self.size = len(vars)
         self.ptr = <SCIP_VAR**> malloc(self.size * sizeof(SCIP_VAR*)) if self.size else NULL
-        for i, var in enumerate(np.ravel(vars)):
+        for i, var in enumerate(vars):
             if not isinstance(var, Variable):
                 raise TypeError(f"Expected Variable, got {type(var)}.")
             self.ptr[i] = (<Variable>var).scip_var