[FIR] KT-54220: Don't crash on unsigned integers when no stdlib present

^KT-54220 Fixed

compiler/fir/analysis-tests/testData/resolveWithStdlib/kt54220.kt

@@ -0,0 +1,6 @@
+const val c = <!CONST_VAL_WITH_NON_CONST_INITIALIZER!>1u + 2u<!>
+
+fun box() = when {
+    c != 3u -> "fail"
+    else -> "OK"
+}