Having fancy graphics on will fix the bug thanks to Mega_Spud for telling me. I was going to remove the addition but credit is a thing so...
Addition by [Minecraft] Mega_Spud (Jay Wells)
This is a known issue that occurs when Fancy Graphics are Off
EDIT: : In 22.214.171.124(build3) the issue is fixed or at least for me.
Steps To Reproduce
0. Turn off fancy graphics if enabled.
1. Do /locate stronghold
2. Find End Portal.
3. Place all but one Ender Eye.
4. Place final one and ta-da. "Unfortunately Minecraft PE has crashed."
For now, the fix is to enable Fancy Graphics which could be a somewhat disappointing bug for slower devices.
1. Open Settings > Video
2. Check "Fancy Graphics"
3. Do Step of 1 of Steps To Reproduce
Also as mentioned by Yanbar
If you stand inside of the portal while putting in the eyes of ender.
You will go the End just like normal ! Which I can imagine REALLY helps slower devices.