Fix bitshift overflow

src/storm/utility/bitoperations.h

@@ -9,7 +9,7 @@
 inline uint64_t smallestIntWithNBitsSet(uint64_t n) {
     STORM_LOG_ASSERT(n < 64, "Input is too large.");
     if (n == 0) return 0;
-    return (1 << n) - 1;
+    return (1ul << n) - 1;
 }
 
 /**