Fix ravel model behaviour to properly clip OOB coordinates

changelog/751.bugfix.rst

@@ -0,0 +1 @@
+Fix coordinate clipping behaviour of Ravel model.

dkist/wcs/models.py

@@ -739,17 +739,19 @@ def evaluate(self, *inputs_):
         # round the index values, but clip them if they exceed the array bounds
         # the bounds are one less than the shape dimension value
         array_bounds = np.array(self.array_shape) - 1
-        rounded_inputs = np.clip(np.rint(input_values).astype(int), None, array_bounds[:, np.newaxis])
-        result = np.ravel_multi_index(rounded_inputs, self.array_shape, order=self.order).astype(float)
+        rounded_inputs = np.rint(input_values).astype(int)
+        result = np.ravel_multi_index(rounded_inputs, self.array_shape, order=self.order, mode="clip").astype(float)
         index = 0 if self.order == "F" else -1
         # Adjust the result to allow a fractional part for interpolation in Tabular1D
         fraction = input_values[index] - rounded_inputs[index]
         result += fraction
+        oob = np.logical_or((rounded_inputs < 0), (rounded_inputs > array_bounds[:, np.newaxis])).any(axis=0)
+        result[oob] = np.nan
         # Put the units back if they were there...
         if has_units:
             result = result * u.pix
         else:
-            result = np.array([result])
+            result = np.array(result)
         return result
 
     @property