Fix compiler bootstrap (1.4.0-dev-9205)

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/IfNullExpressionsFusionLowering.kt

@@ -177,16 +177,13 @@ class IfNullExpressionsFusionLowering(val context: CommonBackendContext) : FileL
         return IfNullExpr(whenExpr.type, subjectVar, branch0.result, elseResult)
     }
 
-    private fun IrBranch.getElseBranchResultOrNull() =
+    private fun IrBranch.getElseBranchResultOrNull(): IrExpression? {
-        when {
+        val branchCondition = condition
-            this is IrElseBranch ->
+        return if (branchCondition is IrConst<*> && branchCondition.value == true)
-                result
+            result
-            // deserialization generates a simple branch with const 'true' condition
+        else
-            condition is IrConst<*> && condition.value == true ->
+            null
-                result
+    }
-            else ->
-                null
-        }
 
     private fun IrExpression.isTrivial() =
         this is IrExpressionWithCopy