Extract Function: Fix NPE when extracting this in object

#KT-6238 Fixed

idea/src/org/jetbrains/jet/plugin/refactoring/extractFunction/ExtractableCodeDescriptor.kt

@@ -120,6 +120,11 @@ class AddPrefixReplacement(override val parameter: Parameter): ParameterReplacem
 class FqNameReplacement(val fqName: FqName): Replacement {
     [suppress("PARAMETER_NAME_CHANGED_ON_OVERRIDE")]
     override fun invoke(e: JetElement): JetElement {
+        val thisExpr = e.getParent() as? JetThisExpression
+        if (thisExpr != null) {
+            return thisExpr.replaced(JetPsiFactory(e).createExpression(fqName.asString())).getQualifiedElementSelector()!!
+        }
+
         val newExpr = (e.getReference() as? JetSimpleNameReference)?.bindToFqName(fqName, ShorteningMode.NO_SHORTENING) as JetElement
         return if (newExpr is JetQualifiedExpression) newExpr.getSelectorExpression()!! else newExpr
     }

idea/testData/refactoring/extractFunction/parameters/misc/thisInObject.kt

@@ -0,0 +1,9 @@
+package p
+
+// SIBLING:
+object O {
+    val a = 1
+    fun test() {
+        <selection>this.a</selection>
+    }
+}

idea/testData/refactoring/extractFunction/parameters/misc/thisInObject.kt.after

@@ -0,0 +1,13 @@
+package p
+
+// SIBLING:
+object O {
+    val a = 1
+    fun test() {
+        unit()
+    }
+}
+
+private fun unit() {
+    O.a
+}

idea/tests/org/jetbrains/jet/plugin/refactoring/introduce/introduceVariable/JetExtractionTestGenerated.java

@@ -1625,6 +1625,12 @@ public class JetExtractionTestGenerated extends AbstractJetExtractionTest {
                     doExtractFunctionTest(fileName);
                 }
 
+                @TestMetadata("thisInObject.kt")
+                public void testThisInObject() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/parameters/misc/thisInObject.kt");
+                    doExtractFunctionTest(fileName);
+                }
+
                 @TestMetadata("typeRef.kt")
                 public void testTypeRef() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/parameters/misc/typeRef.kt");