Update pattern_formatter.h

include/spdlog/details/pattern_formatter.h

@@ -98,8 +98,8 @@ private:
     const padding_info &padinfo_;
     fmt::memory_buffer &dest_;
     size_t total_pad_;
-    string_view_t spaces_ = "                                                                "
-                            "                                                                ";
+    string_view_t spaces_ {"                                                                "
+                           "                                                                ", 128};
 };
 
 class flag_formatter