What is this blank space on the Pokemon Summary page?

Solution 1:

Typically, the Map would be there, indicating the rough location of where that Pokemon was caught or its egg was collected.

Source: Viewing a Pokémon’s Summary

However, due to the overwhelming traffic from players, the map and the "footsteps" were removed in order to relieve some of the pressure from Niantic's servers. Both of these features will be added back once the game calms down and Niantic gets more servers to run everything they need.

Solution 2:

When the game first was released, I remember that spot being used for a cropped image of a map to indicate where you caught the Pokémon. However, I just opened the app, and I'm no longer seeing a map either. Probably a bug in the latest version of the app.