Fix potential panic during request parsing

http/request_parser.go

@@ -49,7 +49,11 @@ func ParseRequest(b []byte) ([]store.Statement, error) {
 			return nil, ErrNoStatements
 		}
 
-		stmts[i].SQL = parameterized[i][0].(string)
+		var ok bool
+		stmts[i].SQL, ok = parameterized[i][0].(string)
+		if !ok {
+			return nil, ErrInvalidRequest
+		}
 		if len(parameterized[i]) == 1 {
 			continue
 		}

http/request_parser_test.go

@@ -206,3 +206,20 @@ func Test_MixedInvalidRequest(t *testing.T) {
 		t.Fatal("got unexpected error for invalid request")
 	}
 }
+
+func Test_SingleInvalidTypeRequests(t *testing.T) {
+	_, err := ParseRequest([]byte(fmt.Sprintf(`[1]`)))
+	if err != ErrInvalidRequest {
+		t.Fatal("got unexpected error for invalid request")
+	}
+
+	_, err = ParseRequest([]byte(fmt.Sprintf(`[[1]]`)))
+	if err != ErrInvalidRequest {
+		t.Fatal("got unexpected error for invalid request")
+	}
+
+	_, err = ParseRequest([]byte(fmt.Sprintf(`[[1, "x", 2]]`)))
+	if err != ErrInvalidRequest {
+		t.Fatal("got unexpected error for invalid request")
+	}
+}