Added more tests

tests/ev_str/find_first_empty_query.c

@@ -0,0 +1,17 @@
+#define EV_STR_IMPLEMENTATION
+#include "ev_str.h"
+
+#include <assert.h>
+
+int main(void)
+{
+  evstring text = evstr("abc");
+  evstring query = evstr("");
+
+  evstring_view match = evstring_findFirst(text, query);
+
+  assert(match.len == 0);
+  assert(match.offset == ~0ull);
+
+  return 0;
+}