Added handler for properties with null value when inserting

src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt

@@ -29,7 +29,6 @@ import org.junit.Assert.*
 import java.net.URI
 import java.time.Duration
 import java.time.Period
-import java.util.TimeZone
 
 class AndroidEventTest {
 
@@ -1269,6 +1268,16 @@ 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,

src/androidTest/java/at/bitfire/ical4android/ICalPreprocessorTest.kt

@@ -9,13 +9,13 @@ import at.bitfire.ical4android.validation.FixInvalidUtcOffsetPreprocessor
 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 {
 

src/androidTest/java/at/bitfire/ical4android/LocaleNonWesternDigitsTest.kt

@@ -4,13 +4,13 @@
 
 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 {
 

src/main/java/at/bitfire/ical4android/AndroidEvent.kt

@@ -990,6 +990,10 @@ abstract class AndroidEvent(
     }
 
     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