Don't allow interacting or panning an unavailable remote view

Even if the remote view was unavailable for whatever reason, it was
possible to pan it. This results in a *very* confused user (me, usually)
when the remote view comes back online.

Author: redstrate

ui/remoteviewwidget.cpp

@@ -962,6 +962,12 @@ void RemoteViewWidget::resizeEvent(QResizeEvent *event)
 
 void RemoteViewWidget::mousePressEvent(QMouseEvent *event)
 {
+    // Don't allow panning or interacting with an unavailable remote view.
+    if (!m_frame.isValid()) {
+        QWidget::mousePressEvent(event);
+        return;
+    }
+
     m_currentMousePosition = mapToSource(QPointF(event->pos()));
 
     auto pan = [this, event]() {
@@ -1074,6 +1080,11 @@ void RemoteViewWidget::pickColor() const
 
 void RemoteViewWidget::mouseMoveEvent(QMouseEvent *event)
 {
+    // Don't allow panning or interacting with an unavailable remote view.
+    if (!m_frame.isValid()) {
+        return;
+    }
+
     m_currentMousePosition = mapToSource(QPointF(event->pos()));
 
     auto pan = [this, event]() {