EA-210533: fix NPE in LiftReturnOrAssignmentInspection

It may be still active after its application due to slow IDEA responsiveness
Do not try to apply it again on invalid PSI elements

idea/src/org/jetbrains/kotlin/idea/inspections/LiftReturnOrAssignmentInspection.kt

@@ -93,7 +93,7 @@ class LiftReturnOrAssignmentInspection @JvmOverloads constructor(private val ski
         override fun getFamilyName() = name
 
         override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
-            BranchedFoldingUtils.foldToAssignment(descriptor.psiElement as KtExpression)
+            BranchedFoldingUtils.tryFoldToAssignment(descriptor.psiElement as KtExpression)
         }
     }
 

idea/src/org/jetbrains/kotlin/idea/intentions/branchedTransformations/BranchedFoldingUtils.kt

@@ -183,7 +183,7 @@ object BranchedFoldingUtils {
 
     fun canFoldToReturn(expression: KtExpression?): Boolean = getFoldableReturnNumber(expression) > 0
 
-    fun foldToAssignment(expression: KtExpression) {
+    fun tryFoldToAssignment(expression: KtExpression) {
         var lhs: KtExpression? = null
         var op: String? = null
         val psiFactory = KtPsiFactory(expression)
@@ -214,7 +214,9 @@ object BranchedFoldingUtils {
             }
         }
         lift(expression)
-        expression.replace(psiFactory.createExpressionByPattern("$0 $1 $2", lhs!!, op!!, expression))
+        if (lhs != null && op != null) {
+            expression.replace(psiFactory.createExpressionByPattern("$0 $1 $2", lhs!!, op!!, expression))
+        }
     }
 
     fun foldToReturn(expression: KtExpression): KtExpression {

idea/src/org/jetbrains/kotlin/idea/quickfix/LiftAssignmentOutOfTryFix.kt

@@ -22,7 +22,7 @@ class LiftAssignmentOutOfTryFix(element: KtTryExpression) : KotlinQuickFixAction
 
     override fun invoke(project: Project, editor: Editor?, file: KtFile) {
         val element = element ?: return
-        BranchedFoldingUtils.foldToAssignment(element)
+        BranchedFoldingUtils.tryFoldToAssignment(element)
     }
 
     companion object : KotlinSingleIntentionActionFactory() {

nj2k/nj2k-services/src/org/jetbrains/kotlin/nj2k/postProcessing/processings/inspeсtionLikeProcessings.kt

@@ -491,7 +491,7 @@ class LiftAssignmentInspectionBasedProcessing :
         } ?: false
 
     override fun apply(element: KtExpression) {
-        BranchedFoldingUtils.foldToAssignment(element)
+        BranchedFoldingUtils.tryFoldToAssignment(element)
     }
 }