lib/nfs/FileReader: set `state=IDLE` before invoking callback

Fixes assertion failure if the callback fails.

NEWS

@@ -4,6 +4,8 @@ ver 0.21.23 (not yet released)
 * storage
   - curl: fix corrupt "href" values in the presence of XML entities
   - curl: unescape "href" values
+* input
+  - nfs: fix crash bug
 * decoder
   - gme: adapt to API change in the upcoming version 0.7.0
 * output

src/lib/nfs/FileReader.cxx

@@ -186,6 +186,8 @@ NfsFileReader::OpenCallback(nfsfh *_fh) noexcept
 
 	fh = _fh;
 
+	state = State::IDLE;
+
 	try {
 		connection->Stat(fh, *this);
 	} catch (...) {
@@ -204,13 +206,13 @@ NfsFileReader::StatCallback(const struct stat *st) noexcept
 	assert(fh != nullptr);
 	assert(st != nullptr);
 
+	state = State::IDLE;
+
 	if (!S_ISREG(st->st_mode)) {
 		OnNfsFileError(std::make_exception_ptr(std::runtime_error("Not a regular file")));
 		return;
 	}
 
-	state = State::IDLE;
-
 	OnNfsFileOpen(st->st_size);
 }