Added handler for properties with null value when inserting (#89)

import java.net.URI

import java.time.Duration

import java.time.Period

import java.util.TimeZone

class AndroidEventTest {

        }

    }

    @Test

    fun testBuildUnknownProperty_NoValue() {

        buildEvent(true) {

            unknownProperties += XProperty("ATTACH", ParameterList(), null)

        }.let { result ->

            // The property should not have been added, so the first unknown property should be null

            assertNull(firstUnknownProperty(result))

        }

    }

    private fun firstException(values: ContentValues): ContentValues? {

        val id = values.getAsInteger(Events._ID)

        provider.query(Events.CONTENT_URI.asSyncAdapter(testAccount), null,

import at.bitfire.ical4android.validation.ICalPreprocessor

import io.mockk.mockkObject

import io.mockk.verify

import java.io.InputStreamReader

import java.io.StringReader

import net.fortuna.ical4j.data.CalendarBuilder

import net.fortuna.ical4j.model.Component

import net.fortuna.ical4j.model.component.VEvent

import org.junit.Assert.assertEquals

import org.junit.Test

import java.io.InputStreamReader

import java.io.StringReader

class ICalPreprocessorTest {

package at.bitfire.ical4android

import java.time.ZoneOffset

import java.util.Locale

import net.fortuna.ical4j.model.property.TzOffsetFrom

import org.junit.AfterClass

import org.junit.Assert.assertEquals

import org.junit.BeforeClass

import org.junit.Test

import java.time.ZoneOffset

import java.util.*

class LocaleNonWesternDigitsTest {

    }

    protected open fun insertUnknownProperty(batch: BatchOperation, idxEvent: Int?, property: Property) {

        if (property.value == null) {

            Ical4Android.log.warning("Ignoring unknown property with null value")

            return

        }

        if (property.value.length > UnknownProperty.MAX_UNKNOWN_PROPERTY_SIZE) {

            Ical4Android.log.warning("Ignoring unknown property with ${property.value.length} octets (too long)")

            return