Unable to open application in EM :: javax.el.ELException: oracle.sysman.emSDK.app.exception.EMSystemException

Sometimes, opening a deployed application doesn't appear in EM under soa-infra tree, but exists in the list when you click on the partition. And when you click on the project from the list, it gives an error with a pop-up with a similar error as below

ADF_FACES-60096:Server Exception during PPR, #5[[
javax.el.ELException: oracle.sysman.emSDK.app.exception.EMSystemException
        at javax.el.BeanELResolver.getValue(BeanELResolver.java:298)
        at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:173)
        at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:200)
        at com.sun.el.parser.AstValue.getValue(AstValue.java:138)
        at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:206)
        at org.apache.myfaces.trinidad.bean.FacesBeanImpl.getProperty(FacesBeanImpl.java:68)
        at org.apache.myfaces.trinidad.component.FacesBeanWrapper.getProperty(FacesBeanWrapper.java:58)
        at org.apache.myfaces.trinidad.component.UIXTable$RowKeyFacesBeanWrapper.getProperty(UIXTable.java:630)
        at org.apache.myfaces.trinidad.component.UIXComponentBase.getProperty(UIXComponentBase.java:1353)
        at org.apache.myfaces.trinidad.component.UIXIterator.getValue(UIXIterator.java:722)
        at org.apache.myfaces.trinidad.component.UIXCollection.__flushCachedModel(UIXCollection.java:1438)

Solution :: Just go to console --> Deployments --> stop & start the 'em' application

Now, you'll see all the deployments in the EM soa-infra tree, as well as you'll be able to open the project.