Elizabeth Knowles, Little Oxford Dictionary of Proverbs (2009) doesn't have any relevant proverbs that are native to English, but it does list a closely related proverb, drawn from Swahili:
When elephants fight, it is the grass that gets hurt.
the weak are likely to suffer as a result of the conflicts o the strong and powerful; African proverb (Swahili)
A somewhat similar proverb pointing to the idea that the actual combatants aren't the only ones injured in a fight is this one from Bartlett Whiting, Early American Proverbs and Proverbial Phrases (1977):
When the members quarrel, the whole body must suffer.
And Wolfgang Mieder, The Prentice-Hall Encyclopedia of World Proverbs (1986) offers this proverb to sum up the implications of the preceding two:
Innocence is no protection. English