Guard if no editor is associated with the hover. This happens when the

debug hover is used from a non cdt-editor, e.g. the cdt-lsp editor.

debug/org.eclipse.cdt.debug.ui/src/org/eclipse/cdt/debug/ui/editors/AbstractDebugTextHover.java

@@ -239,7 +239,9 @@ protected String getExpressionText(ITextViewer textViewer, final IRegion hoverRe
 	 *         validated
 	 */
 	private String getExpressionTextFromAST(IDocument document, final IRegion hoverRegion) {
-		ICElement cElement = CDTUITools.getEditorInputCElement(getEditor().getEditorInput());
+		ICElement cElement = getEditor() == null ? null
+				: CDTUITools.getEditorInputCElement(getEditor().getEditorInput());
+
 		if (!(cElement instanceof ITranslationUnit)) {
 			return null;
 		}