[Spellcheck] Don't initialize SpellcheckWordIterator with empty rulesets.

chrome/renderer/spellchecker/spellcheck_worditerator.cc

Index: chrome/renderer/spellchecker/spellcheck_worditerator.cc
diff --git a/chrome/renderer/spellchecker/spellcheck_worditerator.cc b/chrome/renderer/spellchecker/spellcheck_worditerator.cc
index d6e6abe1db9911d2fb172c0fcf3c83c294676ebc..466ac5dd304ee0962e6d270ebb136b0f2e489b5a 100644
--- a/chrome/renderer/spellchecker/spellcheck_worditerator.cc
+++ b/chrome/renderer/spellchecker/spellcheck_worditerator.cc
@@ -312,6 +312,11 @@ bool SpellcheckWordIterator::Initialize(
   UErrorCode open_status = U_ZERO_ERROR;
   UParseError parse_status;
   string16 rule(attribute->GetRuleSet(allow_contraction));
+
+  // If there is no rule set, the attributes were invalid.
+  if (rule.empty())
+    return false;
+
   iterator_ = ubrk_openRules(rule.c_str(), rule.length(), NULL, 0,
                              &parse_status, &open_status);
   if (U_FAILURE(open_status))