Fix ICE stemming from use of unique pointers in unreachable blocks.

Author: jdm

src/rustc/middle/trans/base.rs

@@ -267,7 +267,7 @@ fn malloc_raw_dyn(bcx: block, t: ty::t, heap: heap,
 fn non_gc_box_cast(bcx: block, val: ValueRef) -> ValueRef {
     debug!("non_gc_box_cast");
     add_comment(bcx, ~"non_gc_box_cast");
-    assert(llvm::LLVMGetPointerAddressSpace(val_ty(val)) == gc_box_addrspace);
+    assert(llvm::LLVMGetPointerAddressSpace(val_ty(val)) == gc_box_addrspace || bcx.unreachable);
     let non_gc_t = T_ptr(llvm::LLVMGetElementType(val_ty(val)));
     PointerCast(bcx, val, non_gc_t)
 }

src/test/run-fail/doublefail.rs

@@ -0,0 +1,5 @@
+//error-pattern:One
+fn main() {
+    fail ~"One";
+    fail ~"Two";
+}