archive/List: disallow passing suffix==nullptr to archive_plugin_from_suffix()

src/archive/ArchiveList.cxx

@@ -26,6 +26,7 @@
 #include "plugins/ZzipArchivePlugin.hxx"
 #include "util/Macros.hxx"
 
+#include <assert.h>
 #include <string.h>
 
 const ArchivePlugin *const archive_plugins[] = {
@@ -51,8 +52,7 @@ static bool archive_plugins_enabled[ARRAY_SIZE(archive_plugins) - 1];
 const ArchivePlugin *
 archive_plugin_from_suffix(const char *suffix) noexcept
 {
-	if (suffix == nullptr)
-		return nullptr;
+	assert(suffix != nullptr);
 
 	archive_plugins_for_each_enabled(plugin)
 		if (plugin->suffixes != nullptr &&

src/input/plugins/ArchiveInputPlugin.cxx

@@ -58,6 +58,8 @@ OpenArchiveInputStream(Path path, Mutex &mutex)
 	}
 
 	const char *suffix = Path::FromFS(archive).GetSuffix();
+	if (suffix == nullptr)
+		return nullptr;
 
 	//check which archive plugin to use (by ext)
 	arplug = archive_plugin_from_suffix(suffix);