fix some 'undefined array key' warnings

app/code/core/Mage/Adminhtml/Block/System/Config/Form/Field.php

@@ -83,10 +83,10 @@ public function render(Varien_Data_Form_Element_Abstract $element)
                 $defTextArr = [];
                 foreach ($options as $k => $v) {
                     if ($isMultiple) {
-                        if (is_array($v['value']) && in_array($k, $v['value'])) {
+                        if (array_key_exists('value', $v) && is_array($v['value']) && in_array($k, $v['value'])) {
                             $defTextArr[] = $v['label'];
                         }
-                    } elseif (isset($v['value'])) {
+                    } elseif (array_key_exists('value', $v)) {
                         if ($v['value'] == $defText) {
                             $defTextArr[] = $v['label'];
                             break;

app/code/core/Mage/Adminhtml/Block/Widget/Grid/Column/Filter/Select.php

@@ -54,7 +54,7 @@ protected function _getOptions()
      */
     protected function _renderOption($option, $value)
     {
-        $selected = (($option['value'] == $value && (!is_null($value))) ? ' selected="selected"' : '');
+        $selected = (!is_null($value) && array_key_exists('value', $option) && ($option['value'] == $value)) ? ' selected="selected"' : '';
         return '<option value="' . $this->escapeHtml($option['value']) . '"' . $selected . '>' . $this->escapeHtml($option['label']) . '</option>';
     }
 
@@ -66,7 +66,7 @@ public function getHtml()
         $html = '<select name="' . $this->_getHtmlName() . '" id="' . $this->_getHtmlId() . '" class="no-changes">';
         $value = $this->getValue();
         foreach ($this->_getOptions() as $option) {
-            if (is_array($option['value'])) {
+            if (array_key_exists('value', $option) && is_array($option['value'])) {
                 $html .= '<optgroup label="' . $this->escapeHtml($option['label']) . '">';
                 foreach ($option['value'] as $subOption) {
                     $html .= $this->_renderOption($subOption, $value);