Fix zip digest check

Change-Id: I5c05c485574131d3fbc8cb5af5b1281d12b822ce
diff --git a/twrpDigestDriver.cpp b/twrpDigestDriver.cpp
index 079d0b8..4023c81 100755
--- a/twrpDigestDriver.cpp
+++ b/twrpDigestDriver.cpp
@@ -69,10 +69,12 @@
 #endif
 
 	if (!TWFunc::Path_Exists(digestfile)) {
+		delete digest;
 		if (Filename.find(".zip") == std::string::npos) {
 			gui_msg(Msg(msg::kError, "no_digest_found=No digest file found for '{1}'. Please unselect Enable Digest verification to restore.")(Filename));
+		} else {
+			return true;
 		}
-		delete digest;
 		return false;
 	}