fix #811 nodes rebooting due to invalid printf call, thanks @IZ1IVA

Ouch, this was nasty - printf format string wasn't matching the parameters
passed in causing a NPE due to a missing last param.

I'll investigate why printf format strings were
not being checked by the compiler (normally gcc offers that feature)

src/mesh/mesh-pb-constants.cpp

@@ -18,7 +18,7 @@ size_t pb_encode_to_bytes(uint8_t *destbuf, size_t destbufsize, const pb_msgdesc
 
     pb_ostream_t stream = pb_ostream_from_buffer(destbuf, destbufsize);
     if (!pb_encode(&stream, fields, src_struct)) {
-        DEBUG_MSG("Panic: can't encode protobuf reason='%s', reason=%s\n", PB_GET_ERROR(&stream));
+        DEBUG_MSG("Panic: can't encode protobuf reason='%s'\n", PB_GET_ERROR(&stream));
         assert(0); // If this asser fails it probably means you made a field too large for the max limits specified in mesh.options
     } else {
         return stream.bytes_written;
@@ -30,7 +30,7 @@ bool pb_decode_from_bytes(const uint8_t *srcbuf, size_t srcbufsize, const pb_msg
 {
     pb_istream_t stream = pb_istream_from_buffer(srcbuf, srcbufsize);
     if (!pb_decode(&stream, fields, dest_struct)) {
-        DEBUG_MSG("Error: can't decode protobuf reason='%s', pb_msgdesc 0x%p, reason=%s\n", PB_GET_ERROR(&stream), fields);
+        DEBUG_MSG("Error: can't decode protobuf reason='%s', pb_msgdesc 0x%p\n", PB_GET_ERROR(&stream), fields);
         return false;
     } else {
         return true;