Do not print C++ line numbers for Java logging.

R=jiayl@webrtc.org

Review URL: https://codereview.webrtc.org/1342963002 .

Cr-Commit-Position: refs/heads/master@{#9945}
diff --git a/webrtc/base/logging.cc b/webrtc/base/logging.cc
index 0bc3866..affbb03 100644
--- a/webrtc/base/logging.cc
+++ b/webrtc/base/logging.cc
@@ -132,7 +132,8 @@
     print_stream_ << "[" << std::dec << id << "] ";
   }
 
-  print_stream_ << "(" << FilenameFromPath(file)  << ":" << line << "): ";
+  if (file != NULL)
+    print_stream_ << "(" << FilenameFromPath(file)  << ":" << line << "): ";
 
   if (err_ctx != ERRCTX_NONE) {
     std::ostringstream tmp;