Update x-pack/plugin/esql/qa/testFixtures/src/main/resources/vector-magnitude.csv-spec

Co-authored-by: Carlos Delgado <[email protected]>

Author: svilen-mihaylov-elastic

x-pack/plugin/esql/qa/testFixtures/src/main/resources/vector-magnitude.csv-spec

@@ -73,3 +73,15 @@ magnitude:double
 avg:double | min:double | max:double
 313.692    | 0.0        | 441.673
 ;
+
+magnitudeWithNull
+required_capability: magnitude_scalar_vector_function
+
+row a = 1
+| eval magnitude = v_magnitude(null) 
+| keep magnitude
+;
+
+magnitude:double
+null
+;