Night was beginning on my hardcore survival world while exploring; I wanted to sleep through the night to prevent mobs from spawning, and so placed my bed at a nearby location to prepare for the night. (Which was under the shade of a tree, where a red mushroom was growing)

What I expected to happen was:
The bed to be placed down, possibly 'popping' the mushroom if the nearby light level was too high, due to a block update.

What actually happened was:
The mushroom updated and 'popped' out of the ground; and 'broke' the bed - 'causing the bed to drop as an item, but it left behind the "head" portion of the bed.

Steps to Reproduce:
1. Create/find a dark room (e.g: through the fill command - "/fill ~5 ~3 ~5 ~-5 ~-1 ~-5 minecraft:dirt 0 hollow")
2. Grab a Mushroom (red or brown), a Bed, and a light-generating block (Redstone Lamp, Sea Lantern, Jack o' Lantern, Glowstone, Lava... anything that creates a light level of 15)
3. Place the mushroom, place the light-block 2 blocks away from the mushroom, so that the light level on the mushroom is 13.
4. Cause the mushroom a block update by placing the bed next to the mushroom.
5. Observe:
The mushroom updates, sees that the light level is too high, so drops - expected.
The bed drops as an item, but leaves the "head" of the bed behind - unexpected.

Additional Notes:

• This occurs in both (+/-) X and Z directions
• This only occurs when placing the bed directly adjacent to the mushroom - if you place the bed diagonally, where the "head" of the bed updates the mushroom - the bed will not "drop", and will remain entirely.
• Used 'Night Vision' effect for the screenshots for visibility purposes.
• Happens with crops when they have no light
• Placing a double plant instead of a bed makes the bottom disappear, but the top remains.
• Regardless of the type of double-plant placed (in creative or survival game mode) the remaining 'top' will be the sunflower.
• The "head" of double plants does not appear to update upon placement/destruction of adjacent blocks; however, targeting the "head" and hitting the "use" key will update and remove it.
• The "head" of the bed does update and remove when placing/destroying adjacent blocks - except when placing another bed where the foot of the original bed would be (in any other direction), even if the new 'foot' of the original bed is the "head" of a new bed. The bed, is then considered "complete" and will be exempt from further block placement/destruction until the bed that 'completes' it is removed.
• Destroying any part of the bed while in Creative mode will remove the bed and any 'attached' components. However, destroying the original "head" of the bed while in Survival mode will only remove the 'incomplete' portion of the bed.
• Water/Lava flowing next to the "head" of double plants will not update/remove them.
• Unloading and then reloading the chunks will remove the leftover "head" of double plants, but not of beds. (e.g: By teleporting away then back, or by disconnecting from then reconnecting to the single-player world); Reloading the chunks through the "Reload chunks" debug option ("F3 + A") does not remove the leftover "head" of double-plants.
• Placing the double plant adjacent to the mushroom (at y-1) where the "head" of the double plant updates the mushroom does not cause the mushroom to drop, nor does it affect the double plant.
• The incomplete bed can be used to sleep through the night.