small additional tweak

src/fsfw/globalfunctions/DleParser.cpp

@@ -24,6 +24,9 @@ ReturnValue_t DleParser::passData(const uint8_t* data, size_t len) {
 ReturnValue_t DleParser::parseRingBuf(size_t& readSize) {
   ctx.setType(DleParser::ContextType::NONE);
   size_t availableData = decodeRingBuf.getAvailableReadData();
+  if(availableData == 0) {
+    return NO_PACKET_FOUND;
+  }
   if (availableData > encodedBuf.second) {
     ErrorInfo info;
     info.len = decodeRingBuf.getAvailableReadData();