fix compiletest crash

src/tools/compiletest/src/read2.rs

@@ -83,7 +83,7 @@ fn extend(&mut self, data: &[u8], filter_paths_from_len: &[String]) {
                 }
 
                 let new_len = bytes.len();
-                if *filtered_len <= HEAD_LEN + TAIL_LEN {
+                if (*filtered_len).min(new_len) <= HEAD_LEN + TAIL_LEN {
                     return;
                 }