xpath BUGFIX wrong message format parameter

Fixes #788
diff --git a/src/xpath.c b/src/xpath.c
index ba818ca..69d656c 100644
--- a/src/xpath.c
+++ b/src/xpath.c
@@ -302,8 +302,8 @@
                 tok_type = LYXP_TOKEN_OPERATOR_MATH;
 
             } else if (prev_function_check) {
-                LOGVAL(ctx, LY_VLOG_NONE, NULL, LYVE_XPATH, "Invalid character 0x%x, perhaps \"%.*s\" is supposed to be a function call.",
-                       expr[parsed], &expr[parsed], ret->tok_len[ret->used - 1], &ret->expr[ret->tok_pos[ret->used - 1]]);
+                LOGVAL(ctx, LY_VLOG_NONE, NULL, LYVE_XPATH, "Invalid character 0x%x ('%c'), perhaps \"%.*s\" is supposed to be a function call.",
+                       expr[parsed], expr[parsed], ret->tok_len[ret->used - 1], &ret->expr[ret->tok_pos[ret->used - 1]]);
                 goto error;
             } else {
                 LOGVAL(ctx, LY_VLOG_NONE, NULL, LY_VCODE_XP_INEXPR, parsed + 1, expr);