handle an impossible case consistently with other parts of the library

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@810206 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math/random/RandomDataImpl.java

@@ -241,7 +241,8 @@ public class RandomDataImpl implements RandomData, Serializable {
         try {
             alg = MessageDigest.getInstance("SHA-1");
         } catch (NoSuchAlgorithmException ex) {
-            return null; // gulp FIXME? -- this *should* never fail.
+            // this should never happen
+            throw MathRuntimeException.createInternalError(ex);
         }
         alg.reset();