fix(subsonic): handle empty quoted phrases in FTS5 query and search expression

Signed-off-by: Deluan <deluan@navidrome.org>

persistence/sql_search_fts.go

@@ -134,7 +134,7 @@ func isDottedAbbreviation(w string, subTokens []string) bool {
 // special characters to prevent query injection.
 func buildFTS5Query(userInput string) string {
 	q := strings.TrimSpace(userInput)
-	if q == "" {
+	if q == "" || q == `""` {
 		return ""
 	}
 
@@ -239,7 +239,7 @@ var ftsSearchColumns = map[string]string{
 func ftsSearchExpr(tableName string, s string) Sqlizer {
 	q := buildFTS5Query(s)
 	if q == "" {
-		s = strings.TrimSpace(s)
+		s = strings.TrimSpace(strings.ReplaceAll(s, `"`, ""))
 		if s != "" {
 			log.Trace("Search using LIKE fallback for non-tokenizable query", "table", tableName, "query", s)
 			return likeSearchExpr(tableName, s)

persistence/sql_search_fts_test.go

@@ -49,6 +49,7 @@ var _ = DescribeTable("buildFTS5Query",
 	Entry("preserves quoted abbreviation verbatim", `"R.E.M."`, `"R.E.M."`),
 	Entry("returns empty string for punctuation-only input", "!!!!!!!", ""),
 	Entry("returns empty string for mixed punctuation", "!@#$%^&", ""),
+	Entry("returns empty string for empty quoted phrase", `""`, ""),
 )
 
 var _ = DescribeTable("normalizeForFTS",
@@ -204,6 +205,10 @@ var _ = Describe("ftsSearchExpr", func() {
 		Expect(ftsSearchExpr("media_file", "")).To(BeNil())
 		Expect(ftsSearchExpr("media_file", "   ")).To(BeNil())
 	})
+
+	It("returns nil for empty quoted phrase", func() {
+		Expect(ftsSearchExpr("media_file", `""`)).To(BeNil())
+	})
 })
 
 var _ = Describe("FTS5 Integration Search", func() {