Remove unsound IllegalStateExceptions in Narrow

Summary: These `IllegalStateException`s are actually unsound in presence of `eqwalizer:dynamic/1`, because it can produce types `t` such that `t <: map()` but some children of `t` are not maps.

Reviewed By: ilya-klyuchnikov

Differential Revision: D62582334

fbshipit-source-id: fd119d239e88e6a41b3732c20e7db4b892747b5a

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/Narrow.scala

@@ -477,7 +477,7 @@ class Narrow(pipelineContext: PipelineContext) {
       case NoneType =>
         NoneType
       case _ =>
-        throw new IllegalStateException()
+        NoneType
     }
 
   def setAllFieldsOptional(mapT: Type, newValTy: Option[Type] = None): Type =
@@ -502,7 +502,7 @@ class Narrow(pipelineContext: PipelineContext) {
       case NoneType =>
         NoneType
       case _ =>
-        throw new IllegalStateException()
+        NoneType
     }
 
   def getRecordField(recDecl: RecDeclTyped, recTy: Type, fieldName: String): Type = {