Support codegen of empty while-loop

#KT-3009 In Progress

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

@@ -425,7 +425,11 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
         StackValue conditionValue = gen(expression.getCondition());
         conditionValue.condJump(end, true, v);
 
-        gen(expression.getBody(), Type.VOID_TYPE);
+        JetExpression body = expression.getBody();
+        if (body != null) {
+            gen(body, Type.VOID_TYPE);
+        }
+        
         v.goTo(condition);
 
         v.mark(end);

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

@@ -0,0 +1,9 @@
+fun box(): String {
+    while (false);
+
+    var x = 0
+    while (x++<5);
+    if (x != 6) return "Fail: $x"
+
+    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/emptyIf.kt");
         }
         
+        @TestMetadata("emptyWhile.kt")
+        public void testEmptyWhile() throws Exception {
+            doTest("compiler/testData/codegen/box/controlStructures/emptyWhile.kt");
+        }
+        
         @TestMetadata("finallyOnEmptyReturn.kt")
         public void testFinallyOnEmptyReturn() throws Exception {
             doTest("compiler/testData/codegen/box/controlStructures/finallyOnEmptyReturn.kt");