Program: 86413
Project: 86413
Buggy source:
@Override public void invoke(@NotNull final Project project,final Editor editor,final PsiFile file) throws IncorrectOperationException {
  ApplicationManager.getApplication().invokeLater(new Runnable(){
    @Override public void run(){
      List<PsiFile> javaFiles=FileManager.getAllJavaFiles(GaugeUtil.moduleForPsiElement(file));
      javaFiles.add(0,NEW_FILE_HOLDER);
      ListPopup stepImplChooser=JBPopupFactory.getInstance().createListPopup(new BaseListPopupStep<PsiFile>("String_Node_Str",javaFiles){
        @Override public boolean isSpeedSearchEnabled(){
          return true;
        }
        @Override public PopupStep onChosen(        final PsiFile selectedValue,        boolean finalChoice){
          return doFinalStep(new Runnable(){
            public void run(){
              if (selectedValue == NEW_FILE_HOLDER) {
                createFileAndAddImpl(editor);
              }
 else {
                addImpl(project,selectedValue.getVirtualFile());
              }
            }
          }
);
        }
        @Override public Icon getIconFor(        PsiFile aValue){
          return aValue == null ? AllIcons.Actions.CreateFromUsage : aValue.getIcon(0);
        }
        @NotNull @Override public String getTextFor(        PsiFile value){
          if (value == null) {
            return "String_Node_Str";
          }
 else {
            return getJavaFileName(value);
          }
        }
      }
);
      stepImplChooser.showCenteredInCurrentWindow(step.getProject());
    }
    private String getJavaFileName(    PsiFile value){
      PsiJavaFile javaFile=(PsiJavaFile)value;
      if (!javaFile.getPackageName().equals("String_Node_Str")) {
        return javaFile.getPackageName() + "String_Node_Str" + javaFile.getName();
      }
      return javaFile.getName();
    }
  }
);
}

Fixed version (ground truth):
@Override public void invoke(@NotNull final Project project,final Editor editor,final PsiFile file) throws IncorrectOperationException {
  ApplicationManager.getApplication().invokeLater(new Runnable(){
    @Override public void run(){
      List<PsiFile> javaFiles=FileManager.getAllJavaFiles(GaugeUtil.moduleForPsiElement(file));
      javaFiles.add(0,NEW_FILE_HOLDER);
      ListPopup stepImplChooser=JBPopupFactory.getInstance().createListPopup(new BaseListPopupStep<PsiFile>("String_Node_Str",javaFiles){
        @Override public boolean isSpeedSearchEnabled(){
          return true;
        }
        @Override public PopupStep onChosen(        final PsiFile selectedValue,        boolean finalChoice){
          return doFinalStep(() -> {
            if (selectedValue == NEW_FILE_HOLDER) {
              createFileAndAddImpl(editor);
            }
 else {
              addImpl(project,selectedValue.getVirtualFile());
            }
          }
);
        }
        @Override public Icon getIconFor(        PsiFile aValue){
          return aValue == null ? AllIcons.Actions.CreateFromUsage : aValue.getIcon(0);
        }
        @NotNull @Override public String getTextFor(        PsiFile value){
          if (value == null) {
            return "String_Node_Str";
          }
 else {
            return getJavaFileName(value);
          }
        }
      }
);
      stepImplChooser.showCenteredInCurrentWindow(step.getProject());
    }
    private String getJavaFileName(    PsiFile value){
      PsiJavaFile javaFile=(PsiJavaFile)value;
      if (!javaFile.getPackageName().equals("String_Node_Str")) {
        return javaFile.getPackageName() + "String_Node_Str" + javaFile.getName();
      }
      return javaFile.getName();
    }
  }
);
}