patch 8.2.3284: no error for insert() or remove() changing a locked blob

Problem:    No error for insert() or remove() changing a locked blob.
Solution:   Check a blob is not locked before changing it. (Sean Dewar,
            closes #8696)
diff --git a/src/proto/blob.pro b/src/proto/blob.pro
index 157f15b..5d80463 100644
--- a/src/proto/blob.pro
+++ b/src/proto/blob.pro
@@ -18,5 +18,5 @@
 int check_blob_index(long bloblen, varnumber_T n1, int quiet);
 int check_blob_range(long bloblen, varnumber_T n1, varnumber_T n2, int quiet);
 int blob_set_range(blob_T *dest, long n1, long n2, typval_T *src);
-void blob_remove(typval_T *argvars, typval_T *rettv);
+void blob_remove(typval_T *argvars, typval_T *rettv, char_u *arg_errmsg);
 /* vim: set ft=c : */