Simplify for: take into account loop parameter nullability

idea/src/org/jetbrains/kotlin/idea/intentions/SimplifyForIntention.kt

@@ -78,7 +78,9 @@ class SimplifyForIntention : SelfTargetingRangeIntention<KtForExpression>(
         val context = element.analyzeFullyAndGetResult().bindingContext
 
         val loopParameterDescriptor = context.get(BindingContext.VALUE_PARAMETER, loopParameter) ?: return null
-        val classDescriptor = loopParameterDescriptor.type.constructor.declarationDescriptor as? ClassDescriptor ?: return null
+        val loopParameterType = loopParameterDescriptor.type
+        if (loopParameterType.isMarkedNullable) return null
+        val classDescriptor = loopParameterType.constructor.declarationDescriptor as? ClassDescriptor ?: return null
 
         var otherUsages = false
         val usagesToRemove : Array<UsageData?>

idea/testData/intentions/iterationOverMap/DataClassNullable.kt

@@ -0,0 +1,11 @@
+// IS_APPLICABLE: false
+// WITH_RUNTIME
+
+data class XY(val x: String, val y: String)
+fun test(xys: Array<XY?>) {
+    for (<caret>xy in xys) {
+        val x = xy?.x
+        val y = xy?.y
+        println(x + y)
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -6555,6 +6555,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("DataClassNullable.kt")
+        public void testDataClassNullable() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/iterationOverMap/DataClassNullable.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("DataClassParametersOrder.kt")
         public void testDataClassParametersOrder() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/iterationOverMap/DataClassParametersOrder.kt");