Fix use-after-free in StorageURL when switching URLs

src/Formats/FormatFactory.h

@@ -153,6 +153,7 @@ public:
     ///  * Parallel reading.
     ///    To enable it, make sure `buf` is a SeekableReadBuffer implementing readBigAt().
     ///  * Parallel parsing.
+    /// `buf` must outlive the returned IInputFormat.
     InputFormatPtr getInput(
         const String & name,
         ReadBuffer & buf,

src/Storages/StorageURL.cpp

@@ -361,6 +361,8 @@ Chunk StorageURLSource::generate()
 
         pipeline->reset();
         reader.reset();
+        input_format.reset();
+        read_buf.reset();
     }
     return {};
 }