Fixed missing middlename action

ref #79

src/components/donations/AddDonationModal.svelte

@@ -209,7 +209,7 @@
                     {#each donors as d}
                       <option value={d.id}>
                         {d.firstname}
-                        {d.middlename}
+                        {d.middlename || ''}
                         {d.lastname}
                       </option>
                     {/each}
@@ -226,7 +226,7 @@
                       {#each runners as r}
                         <option value={r.id}>
                           {r.firstname}
-                          {r.middlename}
+                          {r.middlename || ''}
                           {r.lastname}
                         </option>
                       {/each}

src/components/donations/DonationDetail.svelte

@@ -207,7 +207,7 @@
         {#each current_donors as d}
           <option value={d.id}>
             {d.firstname}
-            {d.middlename}
+            {d.middlename || ''}
             {d.lastname}
           </option>
         {/each}
@@ -224,7 +224,7 @@
           {#each current_runners as r}
             <option value={r.id}>
               {r.firstname}
-              {r.middlename}
+              {r.middlename || ''}
               {r.lastname}
             </option>
           {/each}

src/components/donors/DonorDetail.svelte

@@ -212,7 +212,7 @@
                 .toLocaleString('de-DE', { valute: 'EUR' })}€</a>
           {/if}
         {/each}
-      {:else}Donor has no associated donations.{/if}
+      {:else}{$_('donor-has-no-associated-donations')}{/if}
     </div>
     <div class=" w-full">
       <label