[silgen] check if the body is not null before accessing it

Author: theblixguy

lib/SILGen/SILGenProlog.cpp

@@ -434,9 +434,11 @@ void SILGenFunction::emitProlog(AnyFunctionRef TheClosure,
         unreachableLoc.markAsPrologue();
         B.createUnreachable(unreachableLoc);
 
-        if (!TheClosure.getBody()->getElements().empty()) {
-          auto &ctx = SGM.M.getASTContext();
-          ctx.Diags.diagnose(TheClosure.getBody()->getStartLoc(), diag::unreachable_code_uninhabited_param_note);
+        if (auto body = TheClosure.getBody()) {
+          if (!body->getElements().empty()) {
+            auto &ctx = SGM.M.getASTContext();
+            ctx.Diags.diagnose(body->getStartLoc(), diag::unreachable_code_uninhabited_param_note);
+          }
         }
         break;
       }