Don't show a size until we get the content-length or start getting bytes

Prevents cached lists from showing zero.

src/syncterm/syncterm.c

@@ -1615,6 +1615,7 @@ update_webget_progress(struct webget_request *reqs, size_t items, bool leaveup)
 				pos += added;
 			}
 			else {
+				if (reqs[i].received_size > 0 || reqs[i].remote_size > 0) {
 					char received[10];
 					char total[10];
 					byte_estimate_to_str(reqs[i].received_size, received, sizeof(received), 0, 3);
@@ -1634,6 +1635,7 @@ update_webget_progress(struct webget_request *reqs, size_t items, bool leaveup)
 					}
 				}
 			}
+		}
 		assert_pthread_mutex_unlock(&reqs[i].mtx);
 	}
 	uifc.showbuf(((leaveup && errors) ? 0 : WIN_DYN | WIN_ACT) | WIN_HLP | WIN_SAV | WIN_MID | WIN_IMM,