Require a checksum when writing to SD

From #10204 by @adriancuzman

Marlin/src/gcode/queue.cpp

@@ -341,6 +341,12 @@ inline void get_serial_commands() {
 
           gcode_LastN = gcode_N;
         }
+        #if ENABLED(SDSUPPORT)
+          else if (card.saving) {
+            gcode_line_error(PSTR(MSG_ERR_NO_CHECKSUM));
+            return;
+          }
+        #endif
 
         // Movement commands alert when stopped
         if (IsStopped()) {