Groovy trim function raise an error #2747

I added a Groovy function that check if parameter is not null.
In order to remove spaces and \n I used trim:

groovy:
vars.get("run_cosmo_integration_test").setValue("false");
vars.get("cosmo_unit_tests_success").setValue("false");

cosmo_unit_tests_fail=vars.get("cosmo_unit_tests_fail");
logger.info("cosmo_unit_tests_fail="+cosmo_unit_tests_fail+"end");

if (cosmo_unit_tests_fail.trim().empty)
{

logger.info("*******cosmo_unit_tests_fail is null********");
vars.get("cosmo_unit_tests_success").setValue("true");
}
else
{
logger.info("*******cosmo_unit_tests_fail is not null********");
}

I get the following error:

12:37:54,948 [master>cosmo_tests_remote>check_unit_tests_results@pc-lab128:8811] ERROR - Step 'master>cosmo_tests_remote>check_unit_tests_results' is failed.
java.lang.RuntimeException: Failed to evaluate below expression:
groovy:
vars.get("run_cosmo_integration_test").setValue("false");
vars.get("cosmo_unit_tests_success").setValue("false");
cosmo_unit_tests_fail=vars.get("cosmo_unit_tests_fail");
logger.info("cosmo_unit_tests_fail="+cosmo_unit_tests_fail+"end");
if (cosmo_unit_tests_fail.trim().empty)
{

logger.info("*******cosmo_unit_tests_fail is null********");
vars.get("cosmo_unit_tests_success").setValue("true");
}
else
{
logger.info("*******cosmo_unit_tests_fail is not null********");
}
at com.pmease.quickbuild.util.ExceptionUtils.wrapException(ExceptionUtils.java:87)
at com.pmease.quickbuild.DefaultScriptEngine.evaluate(DefaultScriptEngine.java:93)
at com.pmease.quickbuild.plugin.basis.ScriptStep.run(ScriptStep.java:47)
at com.pmease.quickbuild.plugin.basis.ScriptStep$$EnhancerByCGLIB$$9155cf83.CGLIB$run$1(<generated>)
at com.pmease.quickbuild.plugin.basis.ScriptStep$$EnhancerByCGLIB$$9155cf83$$FastClassByCGLIB$$9fbd52f1.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:215)
at com.pmease.quickbuild.DefaultScriptEngine$Interpolator.intercept(DefaultScriptEngine.java:270)
at com.pmease.quickbuild.plugin.basis.ScriptStep$$EnhancerByCGLIB$$9155cf83.run(<generated>)
at com.pmease.quickbuild.stepsupport.Step.execute(Step.java:479)
at com.pmease.quickbuild.stepsupport.StepExecutionJob.executeStepAwareJob(StepExecutionJob.java:29)
at com.pmease.quickbuild.stepsupport.StepAwareJob.executeBuildAwareJob(StepAwareJob.java:47)
at com.pmease.quickbuild.BuildAwareJob.execute(BuildAwareJob.java:61)
at com.pmease.quickbuild.grid.GridJob.run(GridJob.java:78)
at java.lang.Thread.run(Thread.java:744)
Caused by: com.pmease.quickbuild.QuickbuildException: groovy.lang.MissingMethodException: No signature of method: com.pmease.quickbuild.variable.VariableWrapper.trim() is applicable for argument types: () values: []
Possible solutions: wait(), wait(long), grep(java.lang.Object), is(java.lang.Object), print(java.io.PrintWriter), print(java.lang.Object)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:54)
at org.codehaus.groovy.runtime.callsite.PojoMetaClassSite.call(PojoMetaClassSite.java:46)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:40)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:120)
at script13957438748601499023089.run(script13957438748601499023089.groovy:8)
at com.pmease.quickbuild.plugin.basis.BasisPlugin$18.evaluate(BasisPlugin.java:261)
at com.pmease.quickbuild.DefaultScriptEngine.evaluate(DefaultScriptEngine.java:80)
at com.pmease.quickbuild.plugin.basis.ScriptStep.run(ScriptStep.java:47)
at com.pmease.quickbuild.plugin.basis.ScriptStep$$EnhancerByCGLIB$$9155cf83.CGLIB$run$1(<generated>)
at com.pmease.quickbuild.plugin.basis.ScriptStep$$EnhancerByCGLIB$$9155cf83$$FastClassByCGLIB$$9fbd52f1.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:215)
at com.pmease.quickbuild.DefaultScriptEngine$Interpolator.intercept(DefaultScriptEngine.java:270)
at com.pmease.quickbuild.plugin.basis.ScriptStep$$EnhancerByCGLIB$$9155cf83.run(<generated>)
at com.pmease.quickbuild.stepsupport.Step.execute(Step.java:479)
at com.pmease.quickbuild.stepsupport.StepExecutionJob.executeStepAwareJob(StepExecutionJob.java:29)
at com.pmease.quickbuild.stepsupport.StepAwareJob.executeBuildAwareJob(StepAwareJob.java:47)
at com.pmease.quickbuild.BuildAwareJob.execute(BuildAwareJob.java:61)
at com.pmease.quickbuild.grid.GridJob.run(GridJob.java:78)
at java.lang.Thread.run(Thread.java:744)
at com.pmease.quickbuild.plugin.basis.BasisPlugin$18.evaluate(BasisPlugin.java:285)
at com.pmease.quickbuild.DefaultScriptEngine.evaluate(DefaultScriptEngine.java:80)
... 12 more

Please your advice.