Userland: Fix new GCC warnings

Author: https://github.com/gunnarbeutner
Commit: c861195557
Pull-request: https://github.com/SerenityOS/serenity/pull/6552

Userland/Libraries/LibGUI/Label.cpp

@@ -142,7 +142,10 @@ void Label::wrap_text()
         case '\t':
         case ' ': {
             if (start.has_value())
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
                 words.append(m_text.substring(start.value(), i - start.value()));
+#pragma GCC diagnostic pop
             start.clear();
             continue;
         }