[Infer][Java] Prevent assertion failure in jTransStaticField

Summary: @public If we cannot resolve a class name C, assume C.f is not a static final field rather than crashing.

Test Plan: unit tests

infer/src/java/jTransStaticField.ml

@@ -193,16 +193,12 @@ let translate_instr_static_field context callee_procdesc fs field_type loc =
 
 
 let is_static_final_field context cn fs =
-  let node =
   match JClasspath.lookup_node cn (JContext.get_program context) with
-    | None -> assert false
-    | Some n -> n in
+  | None -> false
+  | Some node ->
     try
       let f = Javalib.get_field node fs in
       let is_static = Javalib.is_static_field f in
       let is_final = Javalib.is_final_field f in
       (is_static && is_final)
     with Not_found -> false
-(* assert false *)
-(* TODO: should nornally not be reachable but it appears to be on the *)
-(* standard library. Probably a JBir translation issue *)