resolveHelper: unnecessary nmethod lookup in CodeCache

The code snippet in question was introduced by the PermGen removal commit (JDK-6964458).

src/share/vm/runtime/sharedRuntime.cpp:
1349 if (is_virtual) {
1350 nmethod* nm = callee_nm;
1351 if (nm == NULL) CodeCache::find_blob(caller_frame.pc());
1352 CompiledIC* inline_cache = CompiledIC_before(caller_nm, caller_frame.pc());
1353 if (inline_cache->is_clean()) {
1354 inline_cache->set_to_monomorphic(virtual_call_info);
1355 }
1356 }

Line 1351 has no side-effects and result is not used (it shouldn't be NULL anyway). Proposed fix: Lookup can be turned into an assert that checks if it is indeed the right callee nmethod.