[apps] Prevent duplicating functions to avoid crashing at exit (when

function stores are deleted)

Change-Id: Ia0efb528f02efaaba87eccd48385163b48593387

apps/sequence/sequence_store.cpp

@@ -50,6 +50,7 @@ void SequenceStore::removeFunction(Shared::Function * f) {
   for (int j = i; j<m_numberOfFunctions; j++) {
     m_sequences[j] = m_sequences[j+1];
   }
+  m_sequences[m_numberOfFunctions] = Sequence("", KDColorBlack);
 }
 
 int SequenceStore::maxNumberOfFunctions() {