Fixed bug in using error variable within catch block.

tests/throw.rs

@@ -29,6 +29,50 @@ fn test_try_catch() -> Result<(), Box<EvalAltResult>> {
         123
     );
 
+    #[cfg(not(feature = "no_function"))]
+    assert_eq!(
+        engine.eval::<INT>(
+            "
+                fn foo(x) { try { throw 42; } catch (x) { return x; } }
+                foo(0)
+            "
+        )?,
+        42
+    );
+
+    assert_eq!(
+        engine.eval::<INT>(
+            "
+                let err = 123;
+                let x = 0;
+                try { throw 42; } catch(err) { return err; }
+            "
+        )?,
+        42
+    );
+
+    assert_eq!(
+        engine.eval::<INT>(
+            "
+                let foo = 123;
+                let x = 0;
+                try { throw 42; } catch(err) { return foo; }
+            "
+        )?,
+        123
+    );
+
+    assert_eq!(
+        engine.eval::<INT>(
+            "
+                let foo = 123;
+                let x = 0;
+                try { throw 42; } catch(err) { return err; }
+            "
+        )?,
+        42
+    );
+
     #[cfg(not(feature = "unchecked"))]
     assert!(matches!(
         *engine