This possibly avoids a crash on no-letters input

git-svn-id: https://cld2.googlecode.com/svn/trunk@170 b252ecd4-b096-bf77-eb8e-91563289f87e

internal/getonescriptspan.cc

@@ -1054,7 +1054,9 @@ void ScriptScanner::LowerScriptSpan(LangSpan* span) {
 // Buffer ALWAYS has leading space and trailing space space space NUL
 bool ScriptScanner::GetOneScriptSpanLower(LangSpan* span) {
   bool ok = GetOneScriptSpan(span);
-  LowerScriptSpan(span);
+  if (ok) {
+    LowerScriptSpan(span);
+  }
   return ok;
 }