updated for version 7.3.104

Problem:    Conceal: using Tab for cchar causes problems. (ZyX)
Solution:   Do not accept a control character for cchar.

src/syntax.c

@@ -4537,6 +4537,13 @@ get_syn_options(arg, opt, conceal_char)
 		;
 #endif
 	    }
+#ifdef FEAT_CONCEAL
+	    if (!vim_isprintc_strict(*conceal_char))
+	    {
+		EMSG(_("E844: invalid cchar value"));
+		return NULL;
+	    }
+#endif
 	    arg = skipwhite(arg + 7);
 	}
 	else

src/version.c

@@ -714,6 +714,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    104,
 /**/
     103,
 /**/