Fluid handler items use CapabilityFluidHandler.FLUID_HANDLER_ITEM_CAPABILITY instead of CapabilityFluidHandler.FLUID_HANDLER_CAPABILITY.
I'm not sure exactly what you're doing with the fluid handler item, but you may want to check if the FluidUtil class already has a method that does what you want.
Your onBlockActivated method doesn't override a super method, so it will never be called unless you do so yourself. If you'd annotated the method with @Override, you would have gotten a compilation error telling you this.
Use your IDE to auto-generate override methods with the correct signature and annotation.
I typically don't browse this forum for real bugs as this forum is nothing but people installing mods for incorrect minecraft versions.
So reporting things on github is the way to do.
As for this, it's been fixed: https://github.com/MinecraftForge/MinecraftForge/commit/c0eea379a4cdb8ecc6af7342ba62e0dadc17b3ee