Fixed KT-5809 Code completion after "?." should not include keywords

#KT-5809 Fixed

idea/src/org/jetbrains/jet/plugin/completion/KeywordCompletion.kt

@@ -67,7 +67,8 @@ object KeywordCompletion {
             CommentFilter(),
             ParentFilter(ClassFilter(javaClass<JetLiteralStringTemplateEntry>())),
             ParentFilter(ClassFilter(javaClass<JetConstantExpression>())),
-            LeftNeighbour(TextFilter("."))
+            LeftNeighbour(TextFilter(".")),
+            LeftNeighbour(TextFilter("?."))
     ))
 
     private class CommentFilter() : ElementFilter {

idea/testData/completion/keywords/AfterSafeDot.kt

@@ -0,0 +1,6 @@
+fun foo() {
+    val str : String?
+    str?.<caret>
+}
+
+// NUMBER: 0

idea/tests/org/jetbrains/jet/completion/KeywordCompletionTestGenerated.java

@@ -17,13 +17,9 @@
 package org.jetbrains.jet.completion;
 
 import com.intellij.testFramework.TestDataPath;
-import junit.framework.Test;
-import junit.framework.TestSuite;
-import org.junit.runner.RunWith;
 import org.jetbrains.jet.JetTestUtils;
-import org.jetbrains.jet.test.InnerTestClasses;
 import org.jetbrains.jet.test.TestMetadata;
-import org.jetbrains.jet.JUnit3RunnerWithInners;
+import org.junit.runner.RunWith;
 
 import java.io.File;
 import java.util.regex.Pattern;
@@ -52,6 +48,12 @@ public class KeywordCompletionTestGenerated extends AbstractKeywordCompletionTes
         doTest(fileName);
     }
     
+    @TestMetadata("AfterSafeDot.kt")
+    public void testAfterSafeDot() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/testData/completion/keywords/AfterSafeDot.kt");
+        doTest(fileName);
+    }
+    
     @TestMetadata("AfterSpaceAndDot.kt")
     public void testAfterSpaceAndDot() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("idea/testData/completion/keywords/AfterSpaceAndDot.kt");