rcfile: close off a syntax when a non-syntax command is encountered

The 'color' commands of a syntax definition should not be allowed to
be interspersed with other, non-syntax commands.

This fixes https://savannah.gnu.org/bugs/?56498.

Bug existed since before version 2.6.0.

src/rcfile.c

@@ -379,6 +379,10 @@ void parse_binding(char *ptr, bool dobind)
 	int menu, mask = 0;
 	funcstruct *f;
 
+#ifdef ENABLE_COLOR
+	opensyntax = FALSE;
+#endif
+
 	if (*ptr == '\0') {
 		jot_error(N_("Missing key name"));
 		return;
@@ -1107,6 +1111,10 @@ void parse_rcfile(FILE *rcstream, bool just_syntax, bool intros_only)
 		if (set == 0)
 			continue;
 
+#ifdef ENABLE_COLOR
+		opensyntax = FALSE;
+#endif
+
 		if (*ptr == '\0') {
 			jot_error(N_("Missing option"));
 			continue;