decoder.h: warning cleanup

Fix a compiler warning about a possibly uninitialized variable (the
compiler cannot prove that the variable is always initialized before
use, even though the code logic guarantees it).

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>

Author: pillo79

src/decoder.h

@@ -208,7 +208,7 @@ class RpcDecoder {
 
         size_t bytes_checked = 0;
         size_t container_size;
-        int type;
+        int type = NO_MSG;
         MsgPack::Unpacker unpacker;
 
         while (bytes_checked + offset < _bytes_stored){