Fixed an issue that caused an app crash if the processing of the vide…

…o was cancelled right after it started. This caused the assetWriter of the GPUImageMovieWriter to be in an unknown state instead of a cancelled state.

framework/Source/iOS/GPUImageMovieWriter.m

@@ -267,7 +267,8 @@ - (void)finishRecording;
 
 - (void)finishRecordingWithCompletionHandler:(void (^)(void))handler;
 {
-    if (assetWriter.status == AVAssetWriterStatusCompleted || assetWriter.status == AVAssetWriterStatusCancelled)
+    if (assetWriter.status == AVAssetWriterStatusCompleted || assetWriter.status == AVAssetWriterStatusCancelled
+        || assetWriter.status == AVAssetWriterStatusUnknown)
     {
         return;
     }