Only try to stop video when it *is* a video

// FREEBIE

Signal/src/ViewControllers/MediaDetailViewController.h

@@ -35,7 +35,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)playVideo;
 
 // Stops playback and rewinds
-- (void)stopVideo;
+- (void)stopAnyVideo;
 
 - (void)setShouldHideToolbars:(BOOL)shouldHideToolbars;
 - (void)zoomOutAnimated:(BOOL)isAnimated;

Signal/src/ViewControllers/MediaDetailViewController.m

@@ -81,7 +81,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)dealloc
 {
-    [self stopVideo];
+    [self stopAnyVideo];
 }
 
 - (instancetype)initWithGalleryItemBox:(GalleryItemBox *)galleryItemBox
@@ -576,6 +576,13 @@ NS_ASSUME_NONNULL_BEGIN
     [self.delegate mediaDetailViewController:self isPlayingVideo:NO];
 }
 
+- (void)stopAnyVideo
+{
+    if (self.isVideo) {
+        [self stopVideo];
+    }
+}
+
 - (void)stopVideo
 {
     OWSAssert(self.isVideo);

Signal/src/ViewControllers/MediaPageViewController.swift

@@ -190,7 +190,7 @@ class MediaPageViewController: UIPageViewController, UIPageViewControllerDataSou
     public func didPressAllMediaButton(sender: Any) {
         Logger.debug("\(logTag) in \(#function)")
 
-        currentViewController.stopVideo()
+        currentViewController.stopAnyVideo()
 
         guard let mediaGalleryDataSource = self.mediaGalleryDataSource else {
             owsFail("\(logTag) in \(#function) mediaGalleryDataSource was unexpectedly nil")
@@ -335,10 +335,7 @@ class MediaPageViewController: UIPageViewController, UIPageViewControllerDataSou
             // Do any cleanup for the no-longer visible view controller
             if transitionCompleted {
                 previousPage.zoomOut(animated: false)
-
-                if previousPage.galleryItem.isVideo {
-                    previousPage.stopVideo()
-                }
+                previousPage.stopAnyVideo()
                 updateFooterBarButtonItems(isPlayingVideo: false)
             }
         }