Merge upstream changes from Marlin 2.1.2.5

Marlin/src/gcode/parser.cpp

@@ -115,9 +115,7 @@ void GCodeParser::parse(char *p) {
   reset(); // No codes to report
 
   auto uppercase = [](char c) {
-    if (TERN0(GCODE_CASE_INSENSITIVE, WITHIN(c, 'a', 'z')))
-      c += 'A' - 'a';
-    return c;
+    return TERN0(GCODE_CASE_INSENSITIVE, WITHIN(c, 'a', 'z')) ? c + 'A' - 'a' : c;
   };
 
   // Skip spaces