ublox/helpers: fix propagation of +URAT response parse error

We have been constructing a GError too late, just leaking it instead of
propagating.

src/plugins/ublox/mm-modem-helpers-ublox.c

@@ -1813,14 +1813,13 @@ mm_ublox_parse_urat_read_response (const gchar  *response,
     }
 
 out:
-    if (inner_error) {
-        g_propagate_error (error, inner_error);
-        return FALSE;
-    }
-
     if (allowed == MM_MODEM_MODE_NONE) {
         inner_error = g_error_new (MM_CORE_ERROR, MM_CORE_ERROR_FAILED,
                                    "Couldn't parse +URAT response: %s", response);
+    }
+
+    if (inner_error) {
+        g_propagate_error (error, inner_error);
         return FALSE;
     }