Prevent buf2 buffer overflow by limiting the the amount of bytes printed

src/frontend/plotting/pvec.c

@@ -83,7 +83,8 @@ pvec(struct dvec *d)
 
     if (d->v_numdims > 1) {
         dimstring(d->v_dims, d->v_numdims, buf3);
-        snprintf(buf2, BSIZE_SP, ", dims = [%s]", buf3);
+        size_t icopy = BSIZE_SP - 11;
+        snprintf(buf2, icopy, ", dims = [%s]", buf3);
         strcat(buf, buf2);
     }