debug: Avoid underflow when scanning for landing pad bytes (#2866)

crates/debug/src/transform/expression.rs

@@ -512,9 +512,11 @@ where
             }
         };
     }
+
     // Find all landing pads by scanning bytes, do not care about
     // false location at this moment.
     // Looks hacky but it is fast; does not need to be really exact.
+    if buf.len() > 2 {
         for i in 0..buf.len() - 2 {
             let op = buf[i];
             if op == gimli::constants::DW_OP_bra.0 || op == gimli::constants::DW_OP_skip.0 {
@@ -530,6 +532,8 @@ where
                 }
             }
         }
+    }
+
     while !pc.is_empty() {
         let unread_bytes = pc.len().into_u64();
         if let Some(marker) = jump_targets.get(&unread_bytes) {