Make dropShevronSuffix more explicit about npos handling

The previous implementation relied on substr(0, npos) returning the
entire string, which works but is subtle. This change makes the
behavior explicit by checking for npos and returning the original
string unchanged when no chevron is found.

Author: Mic92

src/libutil/url.cc

@@ -21,6 +21,8 @@ std::regex revRegex(revRegexS, std::regex::ECMAScript);
 static std::string_view dropShevronSuffix(std::string_view url)
 {
     auto shevron = url.rfind("^");
+    if (shevron == std::string_view::npos)
+        return url;
     return url.substr(0, shevron);
 }