Merge pull request #13978 from mantidproject/13976_Convfit_miniplot_show_diff

ConvFit Added Diff data to Mini plot 

MantidQt/CustomInterfaces/src/Indirect/ConvFit.cpp

@@ -993,8 +993,14 @@ void ConvFit::updatePlot() {
       return;
     MatrixWorkspace_sptr ws = boost::dynamic_pointer_cast<MatrixWorkspace>(
         outputGroup->getItem(specNo));
-    if (ws)
+    if (ws) {
       m_uiForm.ppPlot->addSpectrum("Fit", ws, 1, Qt::red);
+      m_uiForm.ppPlot->addSpectrum("Diff", ws, 2, Qt::blue);
+	  if(m_uiForm.ckPlotGuess->isChecked()){
+		  m_uiForm.ppPlot->removeSpectrum("Guess");
+		  m_uiForm.ckPlotGuess->setChecked(false);
+	  }
+    }
   }
 }