push else operands only for IfReachability::Both

Otherwise a Wasm `if` acts similar to a Wasm `block` since it is known upfront that operands are not required to be input twice.

Author: Robbepop

crates/wasmi/src/engine/translator/func2/stack/control.rs

@@ -127,7 +127,9 @@ impl ControlStack {
             label,
             reachability,
         }));
-        self.else_operands.push(else_operands);
+        if matches!(reachability, IfReachability::Both { .. }) {
+            self.else_operands.push(else_operands);
+        }
     }
 
     /// Pushes a new Wasm `else` onto the [`ControlStack`].