checkers: fix sqlQuery panic

If astcast to SelectorExpr failed, funcExpr.Sel will be nil.

Bug reported by @un000

Signed-off-by: Iskander Sharipov <quasilyte@gmail.com>

checkers/sqlQuery_checker.go

@@ -57,6 +57,9 @@ func (c *sqlQueryChecker) VisitStmt(stmt ast.Stmt) {
 }
 
 func (c *sqlQueryChecker) funcIsQuery(funcExpr *ast.SelectorExpr) bool {
+	if funcExpr.Sel == nil {
+		return false
+	}
 	switch funcExpr.Sel.Name {
 	case "Query", "QueryContext":
 		// Stdlib and friends.

checkers/testdata/sqlQuery/negative_tests.go

@@ -4,6 +4,12 @@ import (
 	"database/sql"
 )
 
+func foo() (int, int) { return 0, 0 }
+
+func notQueryCall() {
+	_, _ = foo()
+}
+
 func queryResultIsUsed(db *sql.DB, qe QueryExecer, mydb *myDatabase) {
 	const queryString = "SELECT * FROM users"