FIR: Fix exception caused by empty supertypes of java.lang.Object

compiler/fir/analysis-tests/testData/resolveWithStdlib/j+k/UsingObject.fir.txt

@@ -0,0 +1,14 @@
+FILE: UsingObject.kt
+    public final class A : R|kotlin/Any| {
+        public constructor(): R|A| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final fun foo(): R|A?| {
+        ^foo Null(null)
+    }
+    public final fun main(): R|kotlin/Unit| {
+        lval w: R|kotlin/Any| = R|/foo|() ?: Q|java/lang|.R|java/lang/Object.Object|()
+        R|<local>/w|.R|kotlin/Any.hashCode|()
+    }

compiler/fir/analysis-tests/testData/resolveWithStdlib/j+k/UsingObject.kt

@@ -0,0 +1,8 @@
+class A
+
+fun foo(): A? = null
+
+fun main() {
+    val w = foo() ?: java.lang.Object()
+    w.hashCode()
+}