audioflinger: Fix EffectChain::dump

Fix missing log line in the case when there are no effects in
the chain.

Bug: 118842894
Test: adb shell dumpsys media.audio_flinger
Change-Id: I31fe4760caa61610de4f143b3a6ae185efb55baa
diff --git a/services/audioflinger/Effects.cpp b/services/audioflinger/Effects.cpp
index ecaeb52..2b34267 100644
--- a/services/audioflinger/Effects.cpp
+++ b/services/audioflinger/Effects.cpp
@@ -2335,13 +2335,10 @@
 
 void AudioFlinger::EffectChain::dump(int fd, const Vector<String16>& args)
 {
-    const size_t SIZE = 256;
-    char buffer[SIZE];
     String8 result;
 
-    size_t numEffects = mEffects.size();
-    snprintf(buffer, SIZE, "    %zu effects for session %d\n", numEffects, mSessionId);
-    result.append(buffer);
+    const size_t numEffects = mEffects.size();
+    result.appendFormat("    %zu effects for session %d\n", numEffects, mSessionId);
 
     if (numEffects) {
         bool locked = AudioFlinger::dumpTryLock(mLock);
@@ -2369,6 +2366,8 @@
         if (locked) {
             mLock.unlock();
         }
+    } else {
+        write(fd, result.string(), result.size());
     }
 }