What if a solar flare from the sun knocked out all the electronics or an EMP from nukes

It would only reduce the hash rate (provided by the inter-networked miners). It is not possible/likely for a solar flare to take out the entire planet. A solar flare powerful enough to knock out all electronics on Earth would be an extraordinarily massive event. The scale of such a storm would likely exceed the highest category currently used to classify solar storms, which is the G5 class on the geomagnetic storm scale. G5 storms can cause widespread electrical disruptions and damage to power grids, but a storm capable of disabling all electronics globally would be unprecedented in recorded history (and I'm even referencing geological measurements of solar events hundreds of thousands or even millions of years ago). The likelihood of such an event is extremely low, but its impact would be catastrophic if it were to occur.