Fix conversion of assignment as expression in J2K

Blockless if's and so with assignment as expression inside
should turn into blockful
 #KT-16816 fixed

j2k/testData/fileOrElement/for/assignmentAsExpressionInBody.java

@@ -0,0 +1,7 @@
+public class SomeClass {
+    void doSomeFor() {
+        int a,b;
+        for (int i = 0; i < 10; i++)
+            a = b = i;
+    }
+}