Fix unintendend jump-cuts in auto DJ

This happened because the track is not able to seek exactly to the intro start
point. In this case taking the  start point as end point does not lead to a zero length intro.

src/library/autodj/autodjprocessor.cpp

@@ -1163,8 +1163,6 @@ void AutoDJProcessor::calculateTransition(DeckAttributes* pFromDeck,
         return;
     }
 
-    qDebug() << "player" << pFromDeck->group << "calculateTransition()";
-
     const double fromDeckEndPosition = getEndSecond(pFromDeck);
     const double toDeckEndPosition = getEndSecond(pToDeck);
     // Since the end position is measured in seconds from 0:00 it is also
@@ -1227,16 +1225,15 @@ void AutoDJProcessor::calculateTransition(DeckAttributes* pFromDeck,
         introStart = toDeckPositionSeconds;
     }
 
-    double introEnd = getIntroEndSecond(pToDeck);
-    if (introEnd < introStart) {
-        // introEnd is invalid. Assume a zero length intro.
-        // The introStart is automatically placed by AnalyzerSilence, so use
-        // that as a fallback if the user has not placed introEnd.
-        introEnd = introStart;
+    double introLength = 0;
+    const double introEndSample = pToDeck->introEndPosition();
+    if (introEndSample != Cue::kNoPosition) {
+        const double introEnd = samplePositionToSeconds(introEndSample, pToDeck);
+        if (introStart < introEnd) {
+            introLength = introEnd - introStart;
+        }
     }
 
-    double introLength = introEnd - introStart;
-
     if (sDebug) {
         qDebug() << this << "calculateTransition"
                  << "introLength" << introLength