Fixed ShortenReferences for the case of extension for object

idea/testData/shortenRefs/extensionForObject.dependency.kt

@@ -0,0 +1,5 @@
+package dependency
+
+object AnObject
+
+fun AnObject.extFun(){}

idea/testData/shortenRefs/extensionForObject.kt

@@ -0,0 +1,5 @@
+import dependency.extFun
+
+fun foo() {
+    <selection>dependency.AnObject.extFun()</selection>
+}

idea/testData/shortenRefs/extensionForObject.kt.after

@@ -0,0 +1,6 @@
+import dependency.AnObject
+import dependency.extFun
+
+fun foo() {
+    AnObject.extFun()
+}