Handle situations where an old emoji image is overwritten

src/freedombone-app-pleroma

@@ -96,6 +96,7 @@ function pleroma_setting_emoji {
         image_extension='png'
     fi
     if [ ! $image_extension ]; then
+        echo $'Invalid image type'
         return
     fi
 
@@ -104,10 +105,15 @@ function pleroma_setting_emoji {
     fi
 
     image_filename=$PLEROMA_DIR/priv/static/emoji/${shortcode}.${image_extension}
+    if [ -f "$image_filename" ]; then
+        mv "$image_filename" "${image_filename}.prev"
+    fi
     wget "$image_url" -O "$image_filename"
     if [ ! -f "$image_filename" ]; then
+        mv "${image_filename}.prev" "${image_filename}"
         return
     fi
+    rm "${image_filename}.prev"
 
     if [[ "$image_url" == *'.jpg' || "$image_url" == *'.jpeg' || "$image_url" == *'.gif' ]]; then
         convert "$image_filename" -resize "$emoji_resolution" "$PLEROMA_DIR/priv/static/emoji/${shortcode}.png"
@@ -786,8 +792,12 @@ function pleroma_add_emoji {
     fi
 
     image_filename=$PLEROMA_DIR/priv/static/emoji/${shortcode}.${image_extension}
+    if [ -f "$image_filename" ]; then
+        mv "$image_filename" "${image_filename}.prev"
+    fi
     wget "$image_url" -O "$image_filename"
     if [ ! -f "$image_filename" ]; then
+        mv "${image_filename}.prev" "${image_filename}"
         dialog --title $"Add Custom Emoji" \
                --msgbox $"Unable to download the image" 6 60
         return