needless_collect: use node_type_opt instead of node_type

It may prevent future ICEs.

Author: mgacek8

clippy_lints/src/loops/needless_collect.rs

@@ -27,7 +27,7 @@ fn check_needless_collect_direct_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCont
         if chain_method.ident.name == sym!(collect) && is_trait_method(cx, &args[0], sym::Iterator);
         if let Some(generic_args) = chain_method.args;
         if let Some(GenericArg::Type(ref ty)) = generic_args.args.get(0);
-        let ty = cx.typeck_results().node_type(ty.hir_id);
+        if let Some(ty) = cx.typeck_results().node_type_opt(ty.hir_id);
         if is_type_diagnostic_item(cx, ty, sym::vec_type)
             || is_type_diagnostic_item(cx, ty, sym::vecdeque_type)
             || match_type(cx, ty, &paths::BTREEMAP)
@@ -82,7 +82,7 @@ fn check_needless_collect_indirect_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCo
                 if let ExprKind::MethodCall(method_name, collect_span, &[ref iter_source], ..) = init_expr.kind;
                 if method_name.ident.name == sym!(collect) && is_trait_method(cx, init_expr, sym::Iterator);
                 if let Some(hir_id) = get_hir_id(*ty, method_name.args);
-                if let ty = cx.typeck_results().node_type(hir_id);
+                if let Some(ty) = cx.typeck_results().node_type_opt(hir_id);
                 if is_type_diagnostic_item(cx, ty, sym::vec_type) ||
                     is_type_diagnostic_item(cx, ty, sym::vecdeque_type) ||
                     is_type_diagnostic_item(cx, ty, sym::BinaryHeap) ||