Npe fix in Instrumented Process (#1766)

[utbot-rider]
Npe fix in for #1292 -
#1292 (comment),
but this is not fix

Author: Domonion

utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentation.kt

@@ -98,11 +98,11 @@ object UtExecutionInstrumentation : Instrumentation<UtConcreteExecutionResult> {
                 // invariants:
                 // 1. phase must always complete if started as static reset relies on it
                 // 2. phase must be fast as there are no incremental changes
-                postprocessingPhase.savedStatics = preparationPhase.start {
+                postprocessingPhase.setStaticFields(preparationPhase.start {
                     val result = setStaticFields(statics)
                     resetTrace()
                     result
-                }
+                })
 
                 // invocation
                 val concreteResult = executePhaseInTimeout(invocationPhase) {

utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/phases/PostprocessingPhase.kt

@@ -12,16 +12,14 @@ class PostprocessingPhase : ExecutionPhase {
 
     private var savedStaticsInstance: Map<FieldId, Any?>? = null
 
-    var savedStatics: Map<FieldId, Any?>
-        get() = savedStaticsInstance!!
-        set(value) {
-            savedStaticsInstance = value
-        }
+    fun setStaticFields(savedStatics: Map<FieldId, Any?>) {
+        savedStaticsInstance = savedStatics
+    }
 
     override fun wrapError(e: Throwable): ExecutionPhaseException = ExecutionPhaseError(this.javaClass.simpleName, e)
 
     fun resetStaticFields() {
-        savedStatics.forEach { (fieldId, value) ->
+        savedStaticsInstance?.forEach { (fieldId, value) ->
             fieldId.jField.run {
                 withAccessibility {
                     set(null, value)