No null check on Date fields for ContextManagerImpl.persistStepContext()

[markfreeman]

I found an issue while using Date fields. Because no null check is done, if a date field is null, the call to getTime() will throw a null pointer exception. See ContextManagerImpl line 124.

Here's the stack trace:
java.lang.NullPointerException
at org.codepond.wizardroid.persistence.ContextManagerImpl.persistStepContext(ContextManagerImpl.java:124)
at org.codepond.wizardroid.Wizard.goNext(Wizard.java:178)
at org.codepond.wizardroid.layouts.BasicWizardLayout.onClick(BasicWizardLayout.java:83)
at android.view.View.performClick(View.java:4438)
at android.view.View$PerformClick.run(View.java:18422)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)