resolve compilation error about `unsafe` block

src/google/protobuf/compiler/rust/message.cc

@@ -287,21 +287,27 @@ void UpbGeneratedMessageTraitImpls(Context& ctx, const Descriptor& msg) {
       unsafe impl $pbr$::AssociatedMiniTable for $Msg$ {
         #[inline(always)]
         fn mini_table() -> *const $pbr$::upb_MiniTable {
-          $std$::ptr::addr_of!($minitable$)
+          unsafe {
+            $std$::ptr::addr_of!($minitable$)
+          }
         }
       }
 
       unsafe impl $pbr$::AssociatedMiniTable for $Msg$View<'_> {
         #[inline(always)]
         fn mini_table() -> *const $pbr$::upb_MiniTable {
-          $std$::ptr::addr_of!($minitable$)
+          unsafe {
+            $std$::ptr::addr_of!($minitable$)
+          }
         }
       }
 
       unsafe impl $pbr$::AssociatedMiniTable for $Msg$Mut<'_> {
         #[inline(always)]
         fn mini_table() -> *const $pbr$::upb_MiniTable {
-          $std$::ptr::addr_of!($minitable$)
+          unsafe {
+            $std$::ptr::addr_of!($minitable$)
+          }
         }
       }
     )rs");