Don't report "Unsafe call with ? extension receiver" with smart-cast

#KT-29499 Fixed

idea/testData/multiFileInspections/platformExtensionReceiverOfInline/before/ToBoolean/src/Test.kt

@@ -6,6 +6,11 @@ fun test() {
 
     JavaClass.getNull().contentNotInline() // OK
     JavaClass.getMy().contentNonExtensionInlineFun() // OK
+
+    val res = JavaClass.getNull()
+    if (res != null) {
+        res.toBoolean() // OK: KT-29499
+    }
 }
 
 fun String.contentNotInline() {}