Elvis -> if intention: don't introduce new variable when RHS type is Nothing

idea/testData/intentions/branched/elvisToIfThen/assignmentAndError.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+fun foo(list: List<String>): String {
+    val first = list.firstOrNull() ?:<caret> error("empty")
+    return "First length: ${first.length}"
+}

idea/testData/intentions/branched/elvisToIfThen/assignmentAndError.kt.after

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+fun foo(list: List<String>): String {
+    val first = list.firstOrNull()
+    if (first == null) error("empty")
+    return "First length: ${first.length}"
+}