Merge remote-tracking branch 'origin/GP-6755-dragonmacher-dt-preview-fix'

Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/DataTypeManagerPlugin.java

@@ -310,6 +310,7 @@ public class DataTypeManagerPlugin extends ProgramPlugin
 	@Override
 	protected void programActivated(Program program) {
 		program.addListener(this);
+		provider.programActivated(program);
 		dataTypeManagerHandler.programOpened(program);
 		dataTypePropertyManager.programOpened(program);
 	}

Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/DataTypesProvider.java

@@ -544,7 +544,7 @@ public class DataTypesProvider extends ComponentProviderAdapter {
 		DataType dataType = dataTypeNode.getDataType();
 		if (dataType.isDeleted()) {
 			// this can happen during an undo
-			lastPreviewNode = null;
+			clearDataTypePreview();
 			return;
 		}
 
@@ -554,6 +554,11 @@ public class DataTypesProvider extends ComponentProviderAdapter {
 		previewPane.setCaretPosition(0);
 	}
 
+	private void clearDataTypePreview() {
+		lastPreviewNode = null;
+		previewPane.setText("");
+	}
+
 	void dispose() {
 		previewUpdateManager.dispose();
 		archiveGTree.dispose();
@@ -977,6 +982,10 @@ public class DataTypesProvider extends ComponentProviderAdapter {
 		programTreeState.remove(id);
 	}
 
+	void programActivated(Program program) {
+		clearDataTypePreview();
+	}
+
 	void archiveClosed(DataTypeManager dtm) {
 		dataTypeManagerChanged(dtm);
 	}