Adjust PreliminaryLoopVisitor to new contracts of DataFlowInfo

Previously, there was a contract that if it contains some
non-trivial type info it also has it in `completeNullabilityInfo`.

But after two previous changes it became false

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/PreliminaryLoopVisitor.kt

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.types.expressions
 
+import gnu.trove.THashSet
 import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.descriptors.impl.LocalVariableDescriptor
 import org.jetbrains.kotlin.psi.KtLoopExpression
@@ -36,9 +37,12 @@ class PreliminaryLoopVisitor private constructor() : AssignedVariablesSearcher()
         languageVersionSettings: LanguageVersionSettings
     ): DataFlowInfo {
         var resultFlowInfo = dataFlowInfo
-        val nullabilityMap = resultFlowInfo.completeNullabilityInfo
+        val nonTrivialValues = THashSet<DataFlowValue>().apply {
+            addAll(dataFlowInfo.completeNullabilityInfo.iterator().map { it._1 })
+            addAll(dataFlowInfo.completeTypeInfo.iterator().map { it._1 })
+        }
         val valueSetToClear = LinkedHashSet<DataFlowValue>()
-        for (value in nullabilityMap.keySet()) {
+        for (value in nonTrivialValues) {
             // Only stable variables are under interest here
             val identifierInfo = value.identifierInfo
             if (value.kind == DataFlowValue.Kind.STABLE_VARIABLE && identifierInfo is IdentifierInfo.Variable) {