[K2]: compiler crash on unresolved delegated extention receiver

A report of UNRESOLVED_REFERENCE should not be made for elements like
FirImplicitThisReference that don't have a source, as they are implicit.

#KT-65044 Fixed

compiler/fir/analysis-tests/testData/resolve/KT-65044.fir.txt

@@ -0,0 +1,5 @@
+FILE: KT-65044.kt
+    public final val <ERROR TYPE REF: Symbol not found for A>.b: <ERROR TYPE REF: Symbol not found for A?>by <Unresolved name: A>#.<Unresolved name: test>#()
+        public get(): <ERROR TYPE REF: Symbol not found for A?> {
+            ^ D|/b|.<Unresolved name: getValue>#(this@R|/b|, ::R|/b|)
+        }

compiler/fir/analysis-tests/testData/resolve/KT-65044.kt

@@ -0,0 +1 @@
+val <!UNRESOLVED_REFERENCE!>A<!>.b: <!UNRESOLVED_REFERENCE, UNRESOLVED_REFERENCE!>A<!>? by <!UNRESOLVED_REFERENCE!>A<!>.test()