[android] #5631 - add a concrete java exception when creating a marker without the required position field.

[android] #5631 - updated test cases to handle invalid position on a Marker

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/annotations/MarkerOptions.java

@@ -4,6 +4,7 @@ import android.graphics.Bitmap;
 import android.os.Parcel;
 import android.os.Parcelable;
 
+import com.mapbox.mapboxsdk.exceptions.InvalidMarkerPositionException;
 import com.mapbox.mapboxsdk.geometry.LatLng;
 
 
@@ -70,6 +71,10 @@ public final class MarkerOptions extends BaseMarkerOptions<Marker, MarkerOptions
      * @return Marker The build marker
      */
     public Marker getMarker() {
+        if (position == null) {
+            throw new InvalidMarkerPositionException();
+        }
+
         marker.setPosition(position);
         marker.setSnippet(snippet);
         marker.setTitle(title);

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/annotations/MarkerViewOptions.java

@@ -4,6 +4,7 @@ import android.graphics.Bitmap;
 import android.os.Parcel;
 import android.os.Parcelable;
 
+import com.mapbox.mapboxsdk.exceptions.InvalidMarkerPositionException;
 import com.mapbox.mapboxsdk.geometry.LatLng;
 
 /**
@@ -73,6 +74,10 @@ public class MarkerViewOptions extends BaseMarkerViewOptions<MarkerView, MarkerV
 
     @Override
     public MarkerView getMarker() {
+        if (position == null) {
+            throw new InvalidMarkerPositionException();
+        }
+        
         marker.setPosition(position);
         marker.setSnippet(snippet);
         marker.setTitle(title);

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/exceptions/InvalidMarkerPositionException.java

@@ -0,0 +1,10 @@
+package com.mapbox.mapboxsdk.exceptions;
+
+public class InvalidMarkerPositionException extends RuntimeException {
+
+    public InvalidMarkerPositionException() {
+        super("Adding an invalid Marker to a Map. " +
+                "Missing the required position field. " +
+                "Provide a non null LatLng as position to the Marker.");
+    }
+}