Make constructors recognize char[n] vs. char* and avoid strlen calls.

core/src/fpdfdoc/doc_basic.cpp

Index: core/src/fpdfdoc/doc_basic.cpp
diff --git a/core/src/fpdfdoc/doc_basic.cpp b/core/src/fpdfdoc/doc_basic.cpp
index 48f3ccae98aafe7faca0d85742d04bee5414e00a..9206b02850efa553c3f74ee14b104d89285a8c3b 100644
--- a/core/src/fpdfdoc/doc_basic.cpp
+++ b/core/src/fpdfdoc/doc_basic.cpp
@@ -530,7 +530,7 @@ CFX_WideString CPDF_PageLabel::GetLabel(int nPage) const
             if (pLabel->KeyExist(FX_BSTRC("P"))) {
                 wsLabel += pLabel->GetUnicodeText(FX_BSTRC("P"));
             }
-            CFX_ByteString bsNumberingStyle = pLabel->GetString(FX_BSTRC("S"), NULL);
+            CFX_ByteString bsNumberingStyle = pLabel->GetString(FX_BSTRC("S"), CFX_ByteStringC());
             int nLabelNum = nPage - n + pLabel->GetInteger(FX_BSTRC("St"), 1);
             CFX_WideString wsNumPortion = _GetLabelNumPortion(nLabelNum, bsNumberingStyle);
             wsLabel += wsNumPortion;