dwm: Only find secondary_layout if m_layout_click

Secondary layout would not be used otherwise.

src/modules/dwm.cpp

@@ -101,11 +101,14 @@ namespace modules {
         // First layout is treated as default by dwm
         m_default_layout = &m_layouts->at(0);
         m_current_layout = find_layout(m_bar_mon->layout.address.cur);
+
+        if (m_layout_click) {
           m_secondary_layout = find_layout(m_secondary_layout_symbol);
 
           if (m_secondary_layout == nullptr) {
             throw module_error("Secondary layout symbol does not exist");
           }
+        }
 
         // Initialize layout symbol
         update_layout_label(m_bar_mon->layout.symbol.cur);