Avoid using a null alias as an array offset in getAliases()

Misc::getAliases() built a table-alias map with
`$tables[$thisDb][$expr->alias] = $expr->table` for every FROM/JOIN
expression. When a table has no alias, `$expr->alias` is null, so this
used null as an array offset, which is deprecated as of PHP 8.5. The
null-keyed entry was never read back: the only consumer looks up
`$tables[$thisDb][$expr->table]`, whose offset is always a non-empty
string.

Skip expressions without an alias. getAliases() output is unchanged.
Removes the now-resolved PossiblyNullArrayOffset baseline entry and adds
a regression test.

Author: ardittirana

psalm-baseline.xml

@@ -1359,9 +1359,6 @@
     <MixedArrayOffset occurrences="1">
       <code>$tables[$thisDb][$expr-&gt;table]</code>
     </MixedArrayOffset>
-    <PossiblyNullArrayOffset occurrences="1">
-      <code>$tables[$thisDb]</code>
-    </PossiblyNullArrayOffset>
   </file>
   <file src="src/Utils/Query.php">
     <InvalidNullableReturnType occurrences="1">

src/Utils/Misc.php

@@ -68,6 +68,10 @@ public static function getAliases($statement, $database)
                 ];
             }
 
+            if (null === $expr->alias || $expr->alias === '') {
+                continue;
+            }
+
             if (! isset($tables[$thisDb])) {
                 $tables[$thisDb] = [];
             }

tests/Utils/MiscTest.php

@@ -132,6 +132,25 @@ public static function getAliasesProvider(): array
                     ],
                 ],
             ],
+            [
+                'SELECT mytable.a x, o.b y FROM mytable JOIN other o ON o.id = mytable.id',
+                'shop',
+                [
+                    'shop' => [
+                        'alias' => null,
+                        'tables' => [
+                            'mytable' => [
+                                'alias' => null,
+                                'columns' => ['a' => 'x'],
+                            ],
+                            'other' => [
+                                'alias' => 'o',
+                                'columns' => ['b' => 'y'],
+                            ],
+                        ],
+                    ],
+                ],
+            ],
         ];
     }
 }