fix: cast to int64 and add positive nsteps check

Author: lachlangrose

LoopStructural/interpolators/supports/_3d_base_structured.py

@@ -150,7 +150,12 @@ def maximum(self, maximum):
         maximum = np.array(maximum, dtype=float)
         length = maximum - self.origin
         length /= self.step_vector
-        self._nsteps = np.ceil(length).astype(int) + 1
+        self._nsteps = np.ceil(length).astype(np.int64) + 1
+        if np.any(~(self._nsteps > 0)):
+            logger.error(
+                f"Cannot resize the interpolation support. The proposed number of steps is {self._nsteps}, these must be all > 0"
+            )
+            raise ValueError("Cannot resize the interpolation support.")
         self.onGeometryChange()
 
     @property