when "if" or a loop body is deleted, replace it with an empty code block

to preserve PSI-text consistency

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/unwrapIfStatement/afterThen.java

@@ -0,0 +1,8 @@
+// "Remove 'if' statement" "true"
+class X {
+    int m(String s) {
+        if (s.equals("abc")) {
+        }
+        return 1;
+    }
+}