Fail-safe flag parsing in search

output/js/constants.js

@@ -121,6 +121,9 @@ const CODEPOINT_LOWERCASE_A = 0x61;
  */
 export function flagToLanguageAscii(flag) {
 	const regionalIndicators = [0, 2].map(idx => flag.codePointAt(idx));
+	if (regionalIndicators.includes(undefined)) {
+		return "";
+	}
 	const ascii = regionalIndicators
 		.map(codePoint => codePoint - CODEPOINT_REGIONAL_INDICATOR_A)
 		.map(codePoint => codePoint + CODEPOINT_LOWERCASE_A)