Fix try catch crasher bug due to null else case.

test/codegen/try_catch.dart

Index: test/codegen/try_catch.dart
diff --git a/test/codegen/try_catch.dart b/test/codegen/try_catch.dart
index 844d7f24d1e59e2e0064a2783467efb0c79c1f11..e124d2263fb11ac10d1c2f04cc445438ed08f7a3 100644
--- a/test/codegen/try_catch.dart
+++ b/test/codegen/try_catch.dart
@@ -10,6 +10,7 @@ foo() {
     rethrow;
   }
 }
+
 bar() {
   try {
     throw "hi there";
@@ -19,7 +20,27 @@ bar() {
     rethrow;
   }
 }
+
+baz() {
+  try {
+    throw "finally only";
+  } finally {
+    return true;
+  }
+}
+
+qux() {
+  try {
+    throw "on only";

[Jacob, 2015/03/27 17:04:30]

code that triggers a NPE without the fix.

+  } on String catch (e, t) {
+    // unreachable
+    rethrow;
+  }
+}
+
 main() {
   foo();
   bar();
+  baz();
+  qux();
 }