prevent null access in value blob. credit: github.com/asg017/pull/23

Author: PThorpe92

src/api.rs

@@ -117,9 +117,13 @@ pub fn mprintf(base: &str) -> Result<*mut c_char, MprintfError> {
 /// Returns the [`sqlite3_value_blob`](https://www.sqlite.org/c3ref/value_blob.html) result
 /// from the given sqlite3_value, as a u8 slice.
 pub fn value_blob<'a>(value: &*mut sqlite3_value) -> &'a [u8] {
-    let n = value_bytes(value);
-    let b = unsafe { sqlite3ext_value_blob(value.to_owned()) };
-    return unsafe { from_raw_parts(b.cast::<u8>(), n as usize) };
+    match value_bytes(value) {
+        0 => &[],
+        n => {
+            let b = unsafe { sqlite3ext_value_blob(value.to_owned()) };
+            unsafe { from_raw_parts(b.cast::<u8>(), n as usize) }
+        }
+    }
 }
 
 /// Returns the [`sqlite3_value_bytes`](https://www.sqlite.org/c3ref/value_blob.html) result