Fix M1001 auto-check logic (MarlinFirmware#20456)

Marlin/src/sd/cardreader.cpp

@@ -755,10 +755,10 @@ void CardReader::write_command(char * const buf) {
    *   - After finishing the previous auto#.g file
    *   - From the LCD command to begin the auto#.g files
    *
-   * Return 'true' if there was nothing to do
+   * Return 'true' if an auto file was started
    */
   bool CardReader::autofile_check() {
-    if (!autofile_index) return true;
+    if (!autofile_index) return false;
 
     if (!isMounted())
       mount();
@@ -773,11 +773,11 @@ void CardReader::write_command(char * const buf) {
         cdroot();
         openAndPrintFile(autoname);
         autofile_index++;
-        return false;
+        return true;
       }
     }
     autofile_cancel();
-    return true;
+    return false;
   }
 #endif