ENH: added a test for TrainImagesRegression with no input vector data

Data/Baseline/OTB-Applications/Files/apTvClTrainImagesRegressionNoVD.txt

+io.mse: 241.0461426

Modules/Applications/AppClassification/test/CMakeLists.txt

@@ -871,6 +871,22 @@ if(OTB_USE_OPENCV)
     ${TEMP}/apTvClTrainImagesRegressionModel.txt)
 endif()
 
+if(OTB_USE_OPENCV)
+  otb_test_application(NAME apTvClTrainImagesRegressionNoVD
+    APP  TrainImagesRegression
+    OPTIONS 
+    -io.il ${INPUTDATA}/Classification/QB_1_ortho.tif?&bands=0,1,2
+    -io.ip ${INPUTDATA}/Classification/QB_1_ortho.tif?&bands=3
+    -sample.nt 50
+    -classifier rf
+    -io.out ${TEMP}/apTvClTrainImagesRegressionNoVD.rf
+    -io.mse ${TEMP}/apTvClTrainImagesRegressionNoVD.txt
+    TESTENVOPTIONS ${TEMP}/apTvClTrainImagesRegressionNoVD.txt
+    VALID   ${ascii_comparison}
+    ${OTBAPP_BASELINE_FILES}/apTvClTrainImagesRegressionNoVD.txt
+    ${TEMP}/apTvClTrainImagesRegressionNoVD.txt)
+endif()
+
 #----------- TrainVectorClassifier unsupervised TESTS ----------------
 if(OTB_USE_SHARK)
   otb_test_application(NAME apTvClTrainVectorUnsupervised