Program: 85756
Project: 85756
Buggy source:
private void importEncountered(Import node,LessSource source){
  String filename=conversionUtils.extractFilename(node.getUrlExpression(),problemsHandler);
  if (filename == null) {
    problemsHandler.errorWrongImport(node.getUrlExpression());
    return;
  }
  String urlParams="String_Node_Str";
  int paramsIndx=filename.lastIndexOf("String_Node_Str");
  if (paramsIndx != -1) {
    urlParams=filename.substring(paramsIndx);
    filename=filename.substring(0,paramsIndx);
  }
  if (isCssFile(filename))   return;
  filename=addLessSuffixIfNeeded(filename,urlParams);
  LessSource importedSource;
  try {
    importedSource=source.relativeSource(filename);
  }
 catch (  FileNotFound ex) {
    problemsHandler.errorFileNotFound(node,filename);
    return;
  }
catch (  CannotReadFile e) {
    problemsHandler.errorFileCanNotBeRead(node,filename);
    return;
  }
catch (  StringSourceException ex) {
    problemsHandler.warnLessImportNoBaseDirectory(node.getUrlExpression());
    return;
  }
  if (isImportOnce(node) && alreadyVisited(importedSource)) {
    astManipulator.removeFromBody(node);
    return;
  }
  importedSources.add(importedSource);
  String importedContent;
  try {
    importedContent=importedSource.getContent();
  }
 catch (  FileNotFound e) {
    problemsHandler.errorFileNotFound(node,filename);
    return;
  }
catch (  CannotReadFile e) {
    problemsHandler.errorFileCanNotBeRead(node,filename);
    return;
  }
  StyleSheet importedAst=parseContent(node,importedContent,importedSource);
  solveImports(importedAst,importedSource);
  if (node.hasMediums()) {
    HiddenTokenAwareTree underlyingStructure=node.getUnderlyingStructure();
    Media media=new Media(underlyingStructure);
    media.setMediums(node.getMediums());
    media.setBody(new GeneralBody(underlyingStructure,importedAst.getMembers()));
    media.configureParentToAllChilds();
    astManipulator.replaceInBody(node,media);
  }
 else {
    astManipulator.replaceInBody(node,importedAst.getChilds());
  }
}

Fixed version (ground truth):
public ASTCssNode importEncountered(Import node,LessSource source){
  String filename=conversionUtils.extractFilename(node.getUrlExpression(),problemsHandler);
  if (filename == null) {
    problemsHandler.errorWrongImport(node.getUrlExpression());
    return null;
  }
  String urlParams="String_Node_Str";
  int paramsIndx=filename.lastIndexOf("String_Node_Str");
  if (paramsIndx != -1) {
    urlParams=filename.substring(paramsIndx);
    filename=filename.substring(0,paramsIndx);
  }
  if (isCssFile(filename))   return null;
  filename=addLessSuffixIfNeeded(filename,urlParams);
  LessSource importedSource;
  try {
    importedSource=source.relativeSource(filename);
  }
 catch (  FileNotFound ex) {
    problemsHandler.errorFileNotFound(node,filename);
    return null;
  }
catch (  CannotReadFile e) {
    problemsHandler.errorFileCanNotBeRead(node,filename);
    return null;
  }
catch (  StringSourceException ex) {
    problemsHandler.warnLessImportNoBaseDirectory(node.getUrlExpression());
    return null;
  }
  if (isImportOnce(node) && alreadyVisited(importedSource)) {
    astManipulator.removeFromBody(node);
    return null;
  }
  importedSources.add(importedSource);
  String importedContent;
  try {
    importedContent=importedSource.getContent();
  }
 catch (  FileNotFound e) {
    problemsHandler.errorFileNotFound(node,filename);
    return null;
  }
catch (  CannotReadFile e) {
    problemsHandler.errorFileCanNotBeRead(node,filename);
    return null;
  }
  StyleSheet importedAst=parseContent(node,importedContent,importedSource);
  if (node.hasMediums()) {
    HiddenTokenAwareTree underlyingStructure=node.getUnderlyingStructure();
    StyleSheet result=new StyleSheet(underlyingStructure);
    Media media=new Media(underlyingStructure);
    result.addMember(media);
    media.setParent(result);
    media.setMediums(node.getMediums());
    GeneralBody mediaBody=new GeneralBody(underlyingStructure,importedAst.getMembers());
    media.setBody(mediaBody);
    media.configureParentToAllChilds();
    mediaBody.configureParentToAllChilds();
    astManipulator.replaceInBody(node,media);
    return result;
  }
 else {
    astManipulator.replaceInBody(node,importedAst.getChilds());
  }
  return importedAst;
}