Revert "Add assumptions that the pointer is non-null"

This reverts commit 9bbfd68.

Author: alexcrichton

src/liballoc/rc.rs

@@ -779,26 +779,12 @@ trait RcBoxPtr<T> {
 
 impl<T> RcBoxPtr<T> for Rc<T> {
     #[inline(always)]
-    fn inner(&self) -> &RcBox<T> {
-        unsafe {
-            // Safe to assume this here, as if it weren't true, we'd be breaking
-            // the contract anyway
-            assume(!self._ptr.is_null());
-            &(**self._ptr)
-        }
-    }
+    fn inner(&self) -> &RcBox<T> { unsafe { &(**self._ptr) } }
 }
 
 impl<T> RcBoxPtr<T> for Weak<T> {
     #[inline(always)]
-    fn inner(&self) -> &RcBox<T> {
-        unsafe {
-            // Safe to assume this here, as if it weren't true, we'd be breaking
-            // the contract anyway
-            assume(!self._ptr.is_null());
-            &(**self._ptr)
-        }
-    }
+    fn inner(&self) -> &RcBox<T> { unsafe { &(**self._ptr) } }
 }
 
 #[cfg(test)]