When specifying empty condition in the where condition the code pointed (#61)

to uninitialized memory in the conditionalphrase.cpp 115 line. This
patch fixes it.

src/phrases/conditionalphrase.cpp

@@ -112,7 +112,8 @@ ConditionalPhrase::~ConditionalPhrase()
 ConditionalPhrase &ConditionalPhrase::operator =(const ConditionalPhrase &other)
 {
     data = other.data;
-    data->parents++;
+    if (data)
+        data->parents++;
     return *this;
 }
 

src/phrases/conditionalphrase.h

@@ -36,7 +36,7 @@ ConditionalPhrase operator op(const QVariant &other) \
 class NUT_EXPORT ConditionalPhrase
 {
 public:
-    PhraseData *data;
+    PhraseData *data = nullptr;
 //    QSharedPointer<PhraseData> leftDataPointer;
 //    QSharedPointer<PhraseData> rightDataPointer;
     ConditionalPhrase();