Support codegen of empty for-loop

#KT-3009 Fixed
 EA-35742 fixed

compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -652,7 +652,10 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
         protected abstract void increment(@NotNull Label loopExit);
 
         public void body() {
-            gen(forExpression.getBody(), Type.VOID_TYPE);
+            JetExpression body = forExpression.getBody();
+            if (body != null) {
+                gen(body, Type.VOID_TYPE);
+            }
         }
 
         private void scheduleLeaveVariable(Runnable runnable) {

compiler/testData/codegen/box/controlStructures/emptyFor.kt

@@ -0,0 +1,15 @@
+var index = 0
+
+val iterator = object : Iterator<Int> {
+    override fun hasNext() = index < 5
+    override fun next() = index++
+}
+
+fun box(): String {
+    for (x in 1..5);
+
+    for (x in iterator);
+    if (index != 5) return "Fail: $index"
+
+    return "OK"
+}

compiler/tests/org/jetbrains/jet/codegen/generated/BlackBoxCodegenTestGenerated.java

@@ -1432,6 +1432,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest("compiler/testData/codegen/box/controlStructures/emptyDoWhile.kt");
         }
         
+        @TestMetadata("emptyFor.kt")
+        public void testEmptyFor() throws Exception {
+            doTest("compiler/testData/codegen/box/controlStructures/emptyFor.kt");
+        }
+        
         @TestMetadata("emptyIf.kt")
         public void testEmptyIf() throws Exception {
             doTest("compiler/testData/codegen/box/controlStructures/emptyIf.kt");