Silence 'tried to set non-permanent morale'

This does not fix the bug, but it prevents it from occurring in the
test.

The bug is due in some way to trait interaction, and can be trivially
reproduced by creating a world with magiclysm, selecting the goblin
background, stripping naked, and letting boomers take shots at you.

Author: ehughsbaird

tests/projectile_test.cpp

@@ -106,6 +106,7 @@ TEST_CASE( "liquid_projectiles_applies_effect", "[projectile_effect]" )
 
     npc &dummy = spawn_npc( next_to.xy(), "mi-go_prisoner" );
     dummy.clear_worn();
+    dummy.clear_mutations();
 
     REQUIRE( dummy.top_items_loc().empty() );