[gradle-plugin] Fix KNPE in mpp plugin

samples/calculator/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.2.31'
+    ext.kotlin_version = '1.3-M2'
 
     repositories {
         google()

samples/calculator/build.gradle

@@ -1,3 +1,15 @@
+allprojects {
+    buildscript {
+        repositories {
+            maven { url "http://dl.bintray.com/kotlin/kotlin-eap" }
+        }
+    }
+
+    repositories {
+        maven { url "http://dl.bintray.com/kotlin/kotlin-eap" }
+    }
+}
+
 task build {
     subprojects.each {
         dependsOn("${it.path}:build")

samples/calculator/common/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.2.31'
+    ext.kotlin_version = '1.3-M2'
 
     repositories {
         mavenCentral()

samples/calculator/jvm/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.2.31'
+    ext.kotlin_version = '1.3-M2'
 
     repositories {
         mavenCentral()