ICU-5489 restore a line which was accidentally omitted

X-SVN-Rev: 21843

icu4j/src/com/ibm/icu/text/Bidi.java

@@ -4501,6 +4501,7 @@ public class Bidi {
         if (!IsValidParaOrLine() || run < 0 ||
                 (runCount < 0 && ! BidiLine.getRuns(this)) ||
                 run >= runCount) {
+            throw new IllegalArgumentException("Invalid call to getRunLevel()");
         }
         if (!isGoodLogicalToVisualRunsMap) {
             getLogicalToVisualRunsMap();