Revert "K2: repeat K1 representation for flexible type parameters"

This reverts commit 81414d75

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaTypeConversion.kt

diff --git a/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaTypeConversion.kt b/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaTypeConversion.kt
index 53ac057..fe971fb 100644
--- a/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaTypeConversion.kt
+++ b/compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaTypeConversion.kt
@@ -10,6 +10,7 @@
 import org.jetbrains.kotlin.fir.diagnostics.ConeSimpleDiagnostic
 import org.jetbrains.kotlin.fir.diagnostics.DiagnosticKind
 import org.jetbrains.kotlin.fir.java.enhancement.readOnlyToMutable
+import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeUnresolvedNameError
 import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.builder.buildResolvedTypeRef
@@ -226,7 +227,11 @@
 
         is JavaTypeParameter -> {
             val symbol = javaTypeParameterStack[classifier]
-            ConeTypeParameterTypeImpl(symbol.toLookupTag(), isNullable = lowerBound != null, attributes)
+            if (symbol != null) {
+                ConeTypeParameterTypeImpl(symbol.toLookupTag(), isNullable = lowerBound != null, attributes)
+            } else {
+                ConeErrorType(ConeUnresolvedNameError(classifier.name))
+            }
         }
 
         null -> {