Fix various warnings (#2147)

src/PrecompiledHeader.hpp

@@ -1,5 +1,3 @@
-#pragma once
-
 #ifdef __cplusplus
 #    include <irccommand.h>
 #    include <ircconnection.h>

src/widgets/helper/ChannelView.cpp

@@ -112,8 +112,6 @@ namespace {
 
 ChannelView::ChannelView(BaseWidget *parent)
     : BaseWidget(parent)
-    , sourceChannel_(nullptr)
-    , underlyingChannel_(nullptr)
     , scrollBar_(new Scrollbar(this))
 {
     this->setMouseTracking(true);

src/widgets/helper/ChannelView.hpp

@@ -182,9 +182,9 @@ private:
 
     LimitedQueueSnapshot<MessageLayoutPtr> snapshot_;
 
-    ChannelPtr channel_;
-    ChannelPtr underlyingChannel_;
-    ChannelPtr sourceChannel_;
+    ChannelPtr channel_ = nullptr;
+    ChannelPtr underlyingChannel_ = nullptr;
+    ChannelPtr sourceChannel_ = nullptr;
 
     Scrollbar *scrollBar_;
     EffectLabel *goToBottom_;