Correct deprecated methods in PHP7.4 (#1079)

* runtime/lib/query/Join.php
  implode() was used against the definition (wrong PHP documentation

* runtime/lib/query/ModelCriteria.php
  count() was used on non-countable variable (non-array)

Author: michalmagic42

runtime/lib/query/Join.php

@@ -537,7 +537,7 @@ public function getClause(&$params)
             for ($i = 0; $i < $this->count; $i++) {
                 $conditions [] = $this->getLeftColumn($i) . $this->getOperator($i) . $this->getRightColumn($i);
             }
-            $joinCondition = sprintf('(%s)', implode($conditions, ' AND '));
+            $joinCondition = sprintf('(%s)', implode(' AND ', $conditions));
         } else {
             $joinCondition = '';
             $this->getJoinCondition()->appendPsTo($joinCondition, $params);

runtime/lib/query/ModelCriteria.php

@@ -525,7 +525,7 @@ public function offset($offset)
      */
     public function select($columnArray)
     {
-        if (!count($columnArray) || $columnArray == '') {
+        if (empty(count($columnArray))) {
             throw new PropelException('You must ask for at least one column');
         }