fix: use correct hashes for empty files (#4620)

Signed-off-by: Paweł Pałucha <pawel.palucha@chainguard.dev>

internal/file/digest_test.go

@@ -72,6 +72,37 @@ func TestNewDigestsFromFile(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:    "empty file has valid checksums",
+			fixture: "test-fixtures/empty.txt",
+			hashes:  supportedHashAlgorithms(),
+			want: []file.Digest{
+				{
+					Algorithm: "md5",
+					Value:     "d41d8cd98f00b204e9800998ecf8427e",
+				},
+				{
+					Algorithm: "sha1",
+					Value:     "da39a3ee5e6b4b0d3255bfef95601890afd80709",
+				},
+				{
+					Algorithm: "sha224",
+					Value:     "d14a028c2a3a2bc9476102bb288234c415a2b01f828ea62ac5b3e42f",
+				},
+				{
+					Algorithm: "sha256",
+					Value:     "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+				},
+				{
+					Algorithm: "sha384",
+					Value:     "38b060a751ac96384cd9327eb1b1e36a21fdb71114be07434c0cc7bf63f6e1da274edebfe76f65fbd51ad2f14898b95b",
+				},
+				{
+					Algorithm: "sha512",
+					Value:     "cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce47d0d13c5d85f2b0ff8318d2877eec2f63b931bd47417a81a538327af927da3e",
+				},
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {