fix assertion in Lp1839669

src/engine/enginebuffer.cpp

@@ -1196,15 +1196,24 @@ void EngineBuffer::postProcess(const int iBufferSize) {
 }
 
 void EngineBuffer::updateIndicators(double speed, int iBufferSize) {
-    VERIFY_OR_DEBUG_ASSERT(m_trackSampleRateOld && m_tempo_ratio_old) {
-        // no track loaded, function not called in this case
+    if (!m_trackSampleRateOld) {
+        // This happens if Deck Passthrough is active but no track is loaded.
+        // We skip indicator updates.
         return;
     }
 
     // Increase samplesCalculated by the buffer size
     m_iSamplesSinceLastIndicatorUpdate += iBufferSize;
 
     const double fFractionalPlaypos = fractionalPlayposFromAbsolute(m_filepos_play);
+
+    double ratio = m_tempo_ratio_old;
+    if (ratio == 0.0) {
+        // In case the track is slowed done to zero we will have INF remaining seconds.
+        // We jump back to a rate of 1.0 to show a useful time.
+        ratio = 1.0;
+    }
+
     const double tempoTrackSeconds = m_trackSamplesOld / kSamplesPerFrame
             / m_trackSampleRateOld / m_tempo_ratio_old;
     if(speed > 0 && fFractionalPlaypos == 1.0) {

src/test/durationutiltest.cpp

@@ -1,3 +1,5 @@
+#include <limits>
+
 #include <gtest/gtest.h>
 
 #include "util/duration.h"
@@ -112,6 +114,8 @@ TEST_F(DurationUtilTest, formatTime) {
     formatTime("24:00:00.000", 24 * 3600);
     formatTime("24:00:01.000", 24 * 3600 + 1);
     formatTime("25:00:01.000", 25 * 3600 + 1);
+    formatTime("?", std::numeric_limits<double>::infinity());
+    formatTime("?", -1);
 }
 
 TEST_F(DurationUtilTest, formatSeconds) {

src/util/duration.cpp

@@ -5,6 +5,7 @@
 #include <QTime>
 
 #include "util/assert.h"
+#include "util/fpclassify.h"
 #include "util/math.h"
 
 namespace mixxx {
@@ -26,8 +27,8 @@ QChar DurationBase::kDecimalSeparator = QChar(0x002E);
 
 // static
 QString DurationBase::formatTime(double dSeconds, Precision precision) {
-    if (dSeconds < 0.0) {
-        // negative durations are not supported
+    if (dSeconds < 0.0 || !isfinite(dSeconds)) {
+        // negative durations and infinity or isNaN values are not supported
         return kInvalidDurationString;
     }