Wait until the element in question appears.

This is an attempt to resolve the following problem seen on Jenkins:

org.openqa.selenium.WebDriverException: textarea is null
Command duration or timeout: 53 milliseconds
Build info: version: '2.40.0', revision: '4c5c0568b004f67810ee41c459549aa4b09c651e', time: '2014-02-19 11:13:01'
System info: host: 'jenkins', ip: '192.168.0.115', os.name: 'Linux', os.arch: 'amd64', os.version: '3.9.4-1-mansion', java.version: '1.7.0_51'
Session ID: f7d5f431-8abb-41cc-85c6-8b5f500dcee7
Driver info: org.openqa.selenium.firefox.FirefoxDriver
Capabilities [{platform=LINUX, acceptSslCerts=true, javascriptEnabled=true, cssSelectorsEnabled=true, databaseEnabled=true, browserName=firefox, handlesAlerts=true, browserConnectionEnabled=true, webStorageEnabled=true, nativeEvents=false, rotatable=false, locationContextEnabled=true, applicationCacheEnabled=true, takesScreenshot=true, version=22.0}]
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:193)
	at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:145)
	at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:573)
	at org.openqa.selenium.remote.RemoteWebDriver.executeScript(RemoteWebDriver.java:482)
	at org.jenkinsci.test.acceptance.po.CodeMirror.set(CodeMirror.java:43)
	at org.jenkinsci.test.acceptance.po.Node.runScript(Node.java:49)
	at core.ScriptTest.execute_system_script(ScriptTest.java:31)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.jenkinsci.test.acceptance.junit.JenkinsAcceptanceTestRule$1.evaluate(JenkinsAcceptanceTestRule.java:50)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.apache.maven.surefire.junit4.JUnit4TestSet.execute(JUnit4TestSet.java:53)
	at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:123)
	at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:104)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:164)
	at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:110)
	at org.apache.maven.surefire.booter.SurefireStarter.invokeProvider(SurefireStarter.java:172)
	at org.apache.maven.surefire.booter.SurefireStarter.runSuitesInProcessWhenForked(SurefireStarter.java:104)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:70)
Caused by: org.openqa.selenium.remote.ErrorHandler$UnknownServerException: textarea is null
Build info: version: '2.40.0', revision: '4c5c0568b004f67810ee41c459549aa4b09c651e', time: '2014-02-19 11:13:01'
System info: host: 'jenkins', ip: '192.168.0.115', os.name: 'Linux', os.arch: 'amd64', os.version: '3.9.4-1-mansion', java.version: '1.7.0_51'
Driver info: driver.version: unknown
	at <anonymous class>.anonymous(http://127.0.0.1:50403/script:68)
	at <anonymous class>.handleEvaluateEvent(http://127.0.0.1:50403/script:68)