[FIR] Fix false positive errors on Throws::class, Throws()

^KT-63794 Fixed

compiler/testData/diagnostics/testsWithStdLib/annotations/throws.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+// ISSUE: KT-63794
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 // FILE: main1.kt
 package abc1
@@ -163,3 +164,10 @@ fun foo3() {}
 fun foo5(x: Throws) {}
 fun foo6(x: kotlin.Throws) {}
 fun foo7(x: kotlin.jvm.Throws) {}
+
+// FILE: main10.kt
+
+val x: Throws? = null
+val y = Throws()
+val z = Throws::exceptionClasses
+val w = Throws::class