Fix ubsan errors

Nullptr memcpy, memmove and 36 bit shift of integer.

Change-Id: Ib79c8a98a710d021fc93b6aaec6c0ba9bde5f91e
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qbytearray.cpp

@@ -2285,7 +2285,7 @@ QByteArray QByteArray::repeated(qsizetype times) const
 
 #define REHASH(a) \
     if (ol_minus_1 < sizeof(std::size_t) * CHAR_BIT) \
-        hashHaystack -= (a) << ol_minus_1; \
+        hashHaystack -= std::size_t(a) << ol_minus_1; \
     hashHaystack <<= 1
 
 static inline qsizetype findCharHelper(QByteArrayView haystack, qsizetype from, char needle) noexcept

src/corelib/tools/qarraydataops.h

@@ -1367,6 +1367,8 @@ public:
         Q_ASSERT(!this->isShared() || b == e);
         Q_ASSERT(b <= e);
         Q_ASSERT(size_t(e - b) <= this->allocatedCapacity() - this->size);
+        if (b == e) // short-cut and handling the case b and e == nullptr
+            return;
 
         prepareSpaceForAppend(b, e, e - b);  // ### perf. loss
         Base::insert(GrowsForwardTag{}, this->end(), b, e);
@@ -1397,6 +1399,8 @@ public:
         Q_ASSERT(!this->isShared() || b == e);
         Q_ASSERT(b <= e);
         Q_ASSERT(size_t(e - b) <= this->allocatedCapacity() - this->size);
+        if (b == e) // short-cut and handling the case b and e == nullptr
+            return;
 
         prepareSpaceForAppend(b, e, e - b);  // ### perf. loss
         Base::moveAppend(b, e);
@@ -1421,6 +1425,8 @@ public:
         Q_ASSERT(b <= e);
         Q_ASSERT(e <= where || b > this->end() || where == this->end()); // No overlap or append
         Q_ASSERT(size_t(e - b) <= this->allocatedCapacity() - this->size);
+        if (b == e) // short-cut and handling the case b and e == nullptr
+            return;
 
         if (this->size > 0 && where == this->begin()) {  // prepend case - special space arrangement
             prepareSpaceForPrepend(b, e, e - b);  // ### perf. loss