Fix timestamp chunks warning in Display cue image

plugins/processing/simple-visualisation/src/box-algorithms/ovpCDisplayCueImage.cpp

@@ -51,6 +51,7 @@ namespace OpenViBEPlugins
 		}
 
 		CDisplayCueImage::CDisplayCueImage(void) :
+			m_bHeaderSent(false),
 			m_pBuilderInterface(NULL),
 			m_pMainWindow(NULL),
 			m_pDrawingArea(NULL),
@@ -79,6 +80,7 @@ namespace OpenViBEPlugins
 		{
 			m_uiIdleFuncTag = 0;
 			m_pStimulusSender = NULL;
+			m_bHeaderSent = false;
 			//>>>> Reading Settings:
 
 			//Number of Cues:
@@ -251,6 +253,10 @@ namespace OpenViBEPlugins
 
 		bool CDisplayCueImage::processClock(CMessageClock& rMessageClock)
 		{
+			if (!m_bHeaderSent)
+			{
+				return true;
+			}
 			IBoxIO* l_pBoxIO=getBoxAlgorithmContext()->getDynamicBoxContext();
 			m_oStimulationEncoder.getInputStimulationSet()->clear();
 
@@ -405,6 +411,7 @@ namespace OpenViBEPlugins
 						m_oStimulationEncoder.encodeHeader();
 						l_pBoxIO->markOutputAsReadyToSend(0, m_ui64LastOutputChunkDate,this->getPlayerContext().getCurrentTime());
 						m_ui64LastOutputChunkDate = this->getPlayerContext().getCurrentTime();
+						m_bHeaderSent = true;
 					}
 					if(m_oStimulationDecoder.isBufferReceived())
 					{