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

Source/platform/text/LineEnding.cpp

 /*
  * Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 184 matching lines @@
             *q++ = toEndingChar;
         } else {
             // Leave other characters alone.
             *q++ = c;
         }
     }
 }
 
 CString normalizeLineEndingsToCRLF(const CString& from)
 {
+    if (!from.length())
+        return from;
     CString result;
     CStringBuffer buffer(result);
     internalNormalizeLineEndingsToCRLF(from, buffer);
     return buffer.buffer();
 }
 
 void normalizeLineEndingsToCR(const CString& from, Vector<char>& result)
 {
     normalizeToCROrLF(from, result, true);
 }
 
 void normalizeLineEndingsToLF(const CString& from, Vector<char>& result)
 {
     normalizeToCROrLF(from, result, false);
 }
 
 void normalizeLineEndingsToNative(const CString& from, Vector<char>& result)
 {
 #if OS(WIN)
     VectorCharAppendBuffer buffer(result);
     internalNormalizeLineEndingsToCRLF(from, buffer);
 #else
     normalizeLineEndingsToLF(from, result);
 #endif
 }
 
 } // namespace WebCore