jsoncpp: Add initialization to pacify scanbuild

The scanbuild analysis cannot see that decodeUnicodeEscapeSequence
either initializes the `unicode` argument or returns `false` such
that the code following it runs only if `unicode` is initialized.
Add an explicit initialization to pacify it.

Utilities/cmjsoncpp/src/lib_json/json_reader.cpp

@@ -1728,6 +1728,7 @@ bool OurReader::decodeUnicodeCodePoint(Token& token,
                                     Location end,
                                     unsigned int& unicode) {
 
+  unicode = 0; // Convince scanbuild this is always initialized before use.
   if (!decodeUnicodeEscapeSequence(token, current, end, unicode))
     return false;
   if (unicode >= 0xD800 && unicode <= 0xDBFF) {