CodeEditUtil#removeChildren: fixed nextLeaf determination

Before when removing more than one element, nextLeaf was invalid as well. The invalidation check below did not work as parent might still exist (element might be relinked to dummy file)

Fixes IDEA-187531 "Add on demand static import" with intervening comment and an empty line breaks code

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/addOnDemandStaticImport/afterEndCommentInAnnotation.java

@@ -0,0 +1,9 @@
+// "Add on demand static import for 'java.lang.annotation.ElementType'" "true"
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.*;
+
+@Target({//simple end comment
+        METHOD})
+@interface F {}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/addOnDemandStaticImport/beforeEndCommentInAnnotation.java

@@ -0,0 +1,8 @@
+// "Add on demand static import for 'java.lang.annotation.ElementType'" "true"
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Target;
+
+@Target({Element<caret>Type.//simple end comment
+
+  METHOD})
+@interface F {}