老师好，这里使用mybatis-plus code generator 插件生成代码的时候报错了：

1. 本地链接成功
2. 
3. 代码也生成了，但是报错了：

/**
 * <p>
 * 
 * </p>
 *
 * @author FreeMarker template error (DEBUG mode; use RETHROW in production!):
The following has evaluated to null or missing:
==> author  [in template "templates/entity.java.ftl" at line 21, column 14]

----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${author}  [in template "templates/entity.java.ftl" at line 21, column 12]
----

Java stack trace (for programmers):
----
freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:467)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:389)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:358)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:330)
	at freemarker.core.Environment.visit(Environment.java:336)
	at freemarker.core.Environment.process(Environment.java:309)
	at freemarker.template.Template.process(Template.java:384)
	at com.baomidou.mybatisplus.generator.engine.FreemarkerTemplateEngine.writer(FreemarkerTemplateEngine.java:52)
	at com.baomidou.mybatisplus.generator.engine.AbstractTemplateEngine.batchOutput(AbstractTemplateEngine.java:91)
	at com.baomidou.mybatisplus.generator.AutoGenerator.execute(AutoGenerator.java:103)
	at com.dragon.idea.generator.service.CodeGeneratorService.generator(CodeGeneratorService.java:118)
	at com.dragon.idea.generator.action.CodeGenerateDialogAction.actionPerformed(CodeGenerateDialogAction.java:25)
	at com.intellij.openapi.actionSystem.ex.ActionUtil.lambda$performActionDumbAwareWithCallbacks$4(ActionUtil.java:240)
	at com.intellij.openapi.actionSystem.ex.ActionUtil.performDumbAwareWithCallbacks(ActionUtil.java:261)
	at com.intellij.openapi.actionSystem.ex.ActionUtil.performActionDumbAwareWithCallbacks(ActionUtil.java:240)
	at com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.lambda$performAction$0(ActionMenuItem.java:277)
	at com.intellij.openapi.wm.impl.FocusManagerImpl.runOnOwnContext(FocusManagerImpl.java:236)
	at com.intellij.openapi.wm.impl.IdeFocusManagerImpl.runOnOwnContext(IdeFocusManagerImpl.java:67)
	at com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.performAction(ActionMenuItem.java:269)
	at com.intellij.openapi.actionSystem.impl.ActionMenuItem.lambda$new$0(ActionMenuItem.java:81)
	at com.intellij.openapi.application.TransactionGuardImpl.runWithWritingAllowed(TransactionGuardImpl.java:214)
	at com.intellij.openapi.application.TransactionGuardImpl.access$200(TransactionGuardImpl.java:21)
	at com.intellij.openapi.application.TransactionGuardImpl$2.run(TransactionGuardImpl.java:196)
	at com.intellij.openapi.application.impl.ApplicationImpl.runIntendedWriteActionOnCurrentThread(ApplicationImpl.java:794)
	at com.intellij.openapi.application.impl.ApplicationImpl.lambda$invokeLater$4(ApplicationImpl.java:350)
	at com.intellij.openapi.application.impl.FlushQueue.doRun(FlushQueue.java:84)
	at com.intellij.openapi.application.impl.FlushQueue.runNextEvent(FlushQueue.java:133)
	at com.intellij.openapi.application.impl.FlushQueue.flushNow(FlushQueue.java:46)
	at com.intellij.openapi.application.impl.FlushQueue$FlushNow.run(FlushQueue.java:189)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:776)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:727)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:746)
	at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:885)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:754)
	at com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$6(IdeEventQueue.java:441)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computePrioritized(CoreProgressManager.java:825)
	at com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$7(IdeEventQueue.java:440)
	at com.intellij.openapi.application.impl.ApplicationImpl.runIntendedWriteActionOnCurrentThread(ApplicationImpl.java:794)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:486)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

请问该如何处理哈