Don't crash by form submission in a document with null encoding.

Source/platform/text/LineEnding.cpp

Index: Source/platform/text/LineEnding.cpp
diff --git a/Source/platform/text/LineEnding.cpp b/Source/platform/text/LineEnding.cpp
index eae0ebc55314ed0143d2b133f9b3a483a6591b68..05487b8d61c02fff0d4a6baad47b25a609254591 100644
--- a/Source/platform/text/LineEnding.cpp
+++ b/Source/platform/text/LineEnding.cpp
@@ -202,6 +202,8 @@ void normalizeToCROrLF(const CString& from, Vector<char>& result, bool toCR)
 
 CString normalizeLineEndingsToCRLF(const CString& from)
 {
+    if (!from.length())
+        return from;
     CString result;
     CStringBuffer buffer(result);
     internalNormalizeLineEndingsToCRLF(from, buffer);