videosource: Do not force a seek on init if we can't seek

This was a regression introduced in 6467a17.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

src/core/videosource.cpp

@@ -408,6 +408,11 @@ FFMS_VideoSource::FFMS_VideoSource(const char *SourceFile, FFMS_Index &Index, in
             }
         }
 
+        // If we are in linear no-rewind mode, don't attempt to seek during init.
+        // Bypass the INITIALIZE_SOURCE stage.
+        if (SeekMode < 0)
+            Stage = DecodeStage::INITIALIZE;
+
         // Cannot "output" without doing all other initialization
         // This is the additional mess required for seekmode=-1 to work in a reasonable way
         OutputFrame(DecodeFrame);