Merge #1006

1006: fix 1005 panic sub overflow r=MarkMcCaskey a=pventuzelo

# Description

Fix issue https://github.com/wasmerio/wasmer/issues/1005

# Review

- [x] Add a short description of the the change to the CHANGELOG.md file


Co-authored-by: Patrick Ventuzelo <ventuzelo.patrick@gmail.com>
Co-authored-by: Patrick Ventuzelo <9038181+pventuzelo@users.noreply.github.com>

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## **[Unreleased]**
 
+- [#1006](https://github.com/wasmerio/wasmer/pull/1006) Fix minor panic issue when `wasmer::compile_with` called with llvm backend
 - [#1009](https://github.com/wasmerio/wasmer/pull/1009) Enable LLVM verifier for all tests, add new llvm-backend-tests crate.
 
 ## 0.11.0 - 2019-11-22

lib/llvm-backend/src/state.rs

@@ -336,12 +336,12 @@ impl State {
         &self,
         n: usize,
     ) -> Result<&[(BasicValueEnum, ExtraInfo)], BinaryReaderError> {
-        self.stack
-            .get(self.stack.len() - n..)
-            .ok_or(BinaryReaderError {
+        let new_len = self.stack.len().checked_sub(n).ok_or(BinaryReaderError {
             message: "invalid value stack",
             offset: -1isize as usize,
-            })
+        })?;
+
+        Ok(&self.stack[new_len..])
     }
 
     pub fn popn_save_extra(