Merge pull request #107 from D4N/tiffvisitor_nullptr_check

Use nullptr check instead of assertion, by Raphaël Hertzog

src/tiffvisitor.cpp

@@ -1294,11 +1294,12 @@ namespace Exiv2 {
             }
             uint16_t tag = getUShort(p, byteOrder());
             TiffComponent::AutoPtr tc = TiffCreator::create(tag, object->group());
-            // The assertion typically fails if a component is not configured in
+            if (tc.get()) {
-            // the TIFF structure table
+                tc->setStart(p);
-            assert(tc.get());
+                object->addChild(tc);
-            tc->setStart(p);
+            } else {
-            object->addChild(tc);
+               EXV_WARNING << "Unable to handle tag " << tag << ".\n";
+            }
             p += 12;
         }