Replace wrong button

src/window/picplanner-window.ui

@@ -45,7 +45,7 @@
 							</object>
             </property>
             <child type="start">
-              <object class="GtkToggleButton" id="back_button">
+              <object class="GtkButton" id="back_button">
                 <property name="icon-name">go-previous-symbolic</property>
                 <property name="tooltip-text">Overview</property>
               </object>