🐛 Bug(nevermore): fix prep_fans to validate using a filter before activating it

Fix an overlook where we only check if the nevermore filter fan speed is set above 0 without
checking if we are actually using a nevermore filter

Author: rootiest

print_macros.cfg

@@ -412,7 +412,7 @@ gcode:
     ## Set part-cooling fan (off)
     M107 ; turn off part cooling fan
     ## Set nevermore/filter fan
-    {% if printcfg.nevermore_speed > 0 %} ; if using a nevermore/filter fan
+    {% if printcfg.nevermore == True and printcfg.nevermore_speed > 0 %} ; if using a nevermore/filter fan
         SET_FAN_SPEED FAN={printcfg.nevermore_name} SPEED={printcfg.nevermore_speed} ; set nevermore/filter fan speed
     {% endif %}