fix(modules): Only add reset tag on non-empty modules

Adding the reset tag to empty modules makes polybar add margins and
separators for that empty module.

Fixes #1857

Ref #1596

include/modules/meta/base.inl

@@ -82,9 +82,11 @@ namespace modules {
       m_cache = CAST_MOD(Impl)->get_output();
       // Make sure builder is really empty
       m_builder->flush();
+      if (!m_cache.empty()) {
         // Add a reset tag after the module
         m_builder->control(controltag::R);
         m_cache += m_builder->flush();
+      }
       m_changed = false;
     }
     return m_cache;