PCA - OPLS Group Name must not be null

[eselmeister]

Currently, an assertion fails if at least one sample group name is null.

!ENTRY org.eclipse.ui 4 0 2024-11-22 12:51:57.612
!MESSAGE Unhandled event loop exception
!STACK 0
org.eclipse.core.runtime.AssertionFailedException: null argument:
    at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:92)
    at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:79)
    at org.eclipse.jface.viewers.StructuredViewer.assertElementsNotNull(StructuredViewer.java:538)
    at org.eclipse.jface.viewers.StructuredViewer.getRawChildren(StructuredViewer.java:942)
    at org.eclipse.jface.viewers.StructuredViewer.getFilteredChildren(StructuredViewer.java:849)
    at org.eclipse.jface.viewers.StructuredViewer.getSortedChildren(StructuredViewer.java:1025)
    at org.eclipse.jface.viewers.AbstractListViewer.inputChanged(AbstractListViewer.java:321)
    at org.eclipse.jface.viewers.ContentViewer.setInput(ContentViewer.java:282)
    at org.eclipse.jface.viewers.StructuredViewer.setInput(StructuredViewer.java:1636)
    at org.eclipse.chemclipse.xxd.process.supplier.pca.ui.swt.AnalysisEditorUI.updateWidgets(AnalysisEditorUI.java:681)
    at org.eclipse.chemclipse.xxd.process.supplier.pca.ui.swt.AnalysisEditorUI.updateSampleList(AnalysisEditorUI.java:762)
    at org.eclipse.chemclipse.xxd.process.supplier.pca.ui.swt.AnalysisEditorUI$17.update(AnalysisEditorUI.java:602)
    at org.eclipse.chemclipse.xxd.process.supplier.pca.ui.swt.SamplesListUI.updateContent(SamplesListUI.java:69)
    at org.eclipse.chemclipse.xxd.process.supplier.pca.ui.internal.provider.SamplesEditingSupport.setValue(SamplesEditingSupport.java:104)