Partial fix for KT-14989: Missed null check for platform type

compiler/testData/codegen/boxAgainstJava/platformTypes/kt14989.kt

@@ -0,0 +1,26 @@
+//WITH_RUNTIME
+// FILE: JavaClass.java
+
+public class JavaClass {
+
+    public Double test() {
+        return null;
+    }
+
+}
+
+// FILE: b.kt
+
+fun test(s: Double) {
+
+}
+
+fun box(): String {
+    try {
+        test(JavaClass().test())
+    }
+    catch (e: IllegalStateException) {
+        return "OK"
+    }
+    return "fail"
+}