Anyone else ran into the problem of hammer glitching out and not loading the visuals of your map, a.k.a. not letting you map anymore. If you know how to fix it please message me.
Are you using the hammer.exe in the Team Fortress 2\bin folder? It does matter which one you use, because (for example) the Source SDK hammer is now deprecated and the HL2 version isn't configured for TF2.
Looking at that white line, it seems like your mouse could have sent your camera and views to the borders as Hammer likes to keep the camera moving if you stop the camera while pressing W.
I ran into this recently. Verifying the Team Fortress 2 cache appeared to fix it (Team Fortress 2 > Properties > Local Files > Verify Integrity of Game Cache).
I think this might have happened because Hammer was open while TF2 was updating. The update process would continually restart until I closed Hammer.
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