fix: Add error messages for when the session or expiresAt was missing while making API requests. (#976)

* fix: add error message for when the session is missing

* let request fire with empty session

Author: dshukertjr

packages/supabase/lib/src/auth_http_client.dart

@@ -14,13 +14,15 @@ class AuthHttpClient extends BaseClient {
       try {
         await _auth.refreshSession();
       } catch (error) {
-        // Failed to refresh the token.
-        final isExpiredWithoutMargin = DateTime.now().isAfter(
-            DateTime.fromMillisecondsSinceEpoch(
-                _auth.currentSession!.expiresAt! * 1000));
-        if (isExpiredWithoutMargin) {
-          // Throw the error instead of making an API request with an expired token.
-          rethrow;
+        final expiresAt = _auth.currentSession?.expiresAt;
+        if (expiresAt != null) {
+          // Failed to refresh the token.
+          final isExpiredWithoutMargin = DateTime.now()
+              .isAfter(DateTime.fromMillisecondsSinceEpoch(expiresAt * 1000));
+          if (isExpiredWithoutMargin) {
+            // Throw the error instead of making an API request with an expired token.
+            rethrow;
+          }
         }
       }
     }