JVM IR: Make receiver type of IrGetField not null

otherwise, it will be mapped to inline class type if underlying type
is primitive of nullable.

 #KT-52913 Fixed

compiler/testData/codegen/box/inlineClasses/kt52913.kt

@@ -0,0 +1,25 @@
+// WITH_STDLIB
+// WORKS_WHEN_VALUE_CLASS
+// LANGUAGE: +ValueClasses
+
+interface MyInterface
+
+var value: Any? = null
+
+fun saveValue(a: Any?) {
+    value = a
+}
+
+OPTIONAL_JVM_INLINE_ANNOTATION
+value class MyClass(private val value: Int): MyInterface {
+    fun foo(other: MyInterface) {
+        saveValue((other as? MyClass)?.value)
+    }
+}
+
+fun box(): String {
+    val x = MyClass(5)
+    x.foo(x)
+    if (value != 5) return "FAIL: $value"
+    return "OK"
+}