parser BUGFIX value of enum

If first enum has value negative integer, it does not set value of highest enum.
diff --git a/src/parser_yang.c b/src/parser_yang.c
index 5205082..799cbfb 100644
--- a/src/parser_yang.c
+++ b/src/parser_yang.c
@@ -1439,6 +1439,10 @@
         enm->value = *value;
         enm->flags |= LYS_AUTOASSIGNED;
         (*value)++;
+    } else if (typ->type->info.enums.enm == enm) {
+        /* change value, which is assigned automatically, if first enum has value. */
+        *value = typ->type->info.enums.enm[0].value;
+        (*value)++;
     }
 
     /* check that the value is unique */