KAPT: Fix an ISE when processing unresolved generic types

Error types that are generic could sometimes throw an ISE when
generating the stub.

This fixes KT-43786

plugins/kapt3/kapt3-compiler/testData/converter/kt43786.kt

@@ -0,0 +1,14 @@
+// CORRECT_ERROR_TYPES
+
+@Suppress("UNRESOLVED_REFERENCE")
+class Application {
+    lateinit var _preferencesDataStore: DataStore<Preferences>
+
+    companion object {
+        @JvmStatic
+        fun get(): Application = error()
+
+        @JvmStatic
+        fun getPreferencesDataStore() = get()._preferencesDataStore
+    }
+}