qcam: Fix ViewFinder memory leak

When setting the format on the ViewFinder, a new image_ is allocated.
Any change in format deletes the existing allocation, but it is not
cleaned up on shutdown:

Direct leak of 32 byte(s) in 1 object(s) allocated from:
    #0 0x7f0bf8a7e17f in operator new(unsigned long) (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10e17f)
    #1 0x564c7205f7b0 in ViewFinder::setFormat(unsigned int, unsigned int, unsigned int) ../src/qcam/viewfinder.cpp:43
    #2 0x564c71fec467 in MainWindow::startCapture() ../src/qcam/main_window.cpp:152
    #3 0x564c71fe6c1a in MainWindow::MainWindow(libcamera::CameraManager*, OptionsParser::Options const&) ../src/qcam/main_window.cpp:40
    #4 0x564c71fdf133 in main ../src/qcam/main.cpp:76
    #5 0x7f0bf5944b6a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x26b6a)

Provide a ViewFinder destructor, and delete the allocation as
appropriate.

Fixes: 97e8b3a2eb ("qcam: Add Qt-based GUI application")
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/qcam/viewfinder.cpp

@@ -16,6 +16,11 @@ ViewFinder::ViewFinder(QWidget *parent)
 {
 }
 
+ViewFinder::~ViewFinder()
+{
+	delete image_;
+}
+
 void ViewFinder::display(const unsigned char *raw, size_t size)
 {
 	converter_.convert(raw, size, image_);

src/qcam/viewfinder.h

@@ -17,6 +17,7 @@ class ViewFinder : public QLabel
 {
 public:
 	ViewFinder(QWidget *parent);
+	~ViewFinder();
 
 	int setFormat(unsigned int format, unsigned int width,
 		      unsigned int height);