Refactor of RtpPacket constructor

Bug: None
Change-Id: I869d654cb28bc6d8291d77d6b0c45a68a4232a38
Reviewed-on: https://webrtc-review.googlesource.com/c/107887
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26607}
diff --git a/modules/rtp_rtcp/source/rtp_packet.cc b/modules/rtp_rtcp/source/rtp_packet.cc
index 6f22735..91f0c59 100644
--- a/modules/rtp_rtcp/source/rtp_packet.cc
+++ b/modules/rtp_rtcp/source/rtp_packet.cc
@@ -61,12 +61,10 @@
 RtpPacket::RtpPacket(const RtpPacket&) = default;
 
 RtpPacket::RtpPacket(const ExtensionManager* extensions, size_t capacity)
-    : buffer_(capacity) {
+    : extensions_(extensions ? *extensions : ExtensionManager()),
+      buffer_(capacity) {
   RTC_DCHECK_GE(capacity, kFixedHeaderSize);
   Clear();
-  if (extensions) {
-    extensions_ = *extensions;
-  }
 }
 
 RtpPacket::~RtpPacket() {}