[NI] Remove lambda coersion to Unit in case of error return type(s)

Coersion to Unit from error type leads to misleading type mismatches:
"expected <expected lambda return type> found Unit", despite no user-provided Unit / empty lambda.
These diagnostics were collected, but not reported before, and that had been disguising the issue for a while.

KT-34729 Fixed

compiler/testData/diagnostics/tests/AutoCreatedIt.kt

@@ -10,7 +10,7 @@ fun text() {
     bar1 {1}
     bar1 {it + 1}
 
-    bar2 {<!TYPE_MISMATCH!><!>}
+    bar2 <!NI;TYPE_MISMATCH!>{<!TYPE_MISMATCH!><!>}<!>
     bar2 {1}
     bar2 {<!UNRESOLVED_REFERENCE!>it<!>}
     bar2 <!NI;TYPE_MISMATCH!>{<!CANNOT_INFER_PARAMETER_TYPE, EXPECTED_PARAMETERS_NUMBER_MISMATCH!>it<!> -> <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>it<!>}<!>