Ignore unknown commands if they start with G, M, or T

Marlin/Marlin_main.cpp

@@ -5301,7 +5301,7 @@ void process_next_command() {
         gcode_G92();
         break;
 
-      default: code_is_good = false;
+      // default: code_is_good = false;
     }
     break;
 
@@ -5392,8 +5392,6 @@ void process_next_command() {
         gcode_M109();
         break;
 
-      case 110: break; // M110: Set line number - don't show "unknown command"
-
       #if HAS_TEMP_BED
         case 190: // M190: Wait for bed heater to reach target
           gcode_M190();
@@ -5735,13 +5733,15 @@ void process_next_command() {
         gcode_M999();
         break;
 
-      default: code_is_good = false;
+      // default: code_is_good = false;
     }
     break;
 
     case 'T':
       gcode_T(codenum);
     break;
+
+    default: code_is_good = false;
   }
 
 ExitUnknownCommand: