Fixed error in admin pannel.

Author: alfredsgenkins

src/Model/Block/Source/Block.php

@@ -56,7 +56,11 @@ public function getAllOptions()
                 ];
             }
 
-            array_unshift($this->_options, ['value' => '', 'label' => __('Please select a static block.')]);
+            if (is_array($this->_options)) {
+                array_unshift($this->_options, ['value' => '', 'label' => __('Please select a static block.')]);
+            } else {
+                $this->_options = ['value' => '', 'label' => __('No static blocks to select.')];
+            }
         }
 
         return $this->_options;

src/Model/Menu/Source/Menu.php

@@ -52,7 +52,11 @@ public function getAllOptions()
                 ];
             }
 
-            array_unshift($this->_options, ['value' => '', 'label' => __('Please select a menu.')]);
+            if (is_array($this->_options)) {
+                array_unshift($this->_options, ['value' => '', 'label' => __('Please select a menu.')]);
+            } else {
+                $this->_options = ['value' => '', 'label' => __('No menus to select.')];
+            }
         }
 
         return $this->_options;

src/Model/Product/Attribute/Source/VisibleOnFrontend.php

@@ -65,7 +65,11 @@ public function getAllOptions()
                 ];
             }
 
-            array_unshift($this->_options, ['value' => '', 'label' => __('Please select an attribute.')]);
+            if (is_array($this->_options)) {
+                array_unshift($this->_options, ['value' => '', 'label' => __('Please select an attribute.')]);
+            } else {
+                $this->_options = ['value' => '', 'label' => __('No attributes (visible on frontend) to select.')];
+            }
         }
 
         return $this->_options;