Make sure missing model never becomes null

Author: embeddedt

common/src/main/java/org/embeddedt/modernfix/dynamicresources/DynamicBakedModelProvider.java

@@ -123,6 +123,8 @@ private static boolean isVanillaTopLevelModel(ResourceLocation location) {
                 // can occur if the MRL is not valid for that blockstate, ignore
             }
         }
+        if(location.getNamespace().equals("minecraft") && location.getPath().equals("builtin/missing"))
+            return true;
         return false;
     }