Recovery for initializer if no LBRACE

- If no LBRACE after 'init' keyword parse initializer without body
- Made getBody() nullable, appropriate checks added

compiler/testData/psi/recovery/initRecovery.kt

@@ -0,0 +1,13 @@
+class A {
+    init
+}
+
+class B {
+    Ann init
+    val x = 1
+    init
+    fun foo() {}
+    init
+    init
+    init {}
+}