Hide '0 inputs' badge on problem cards

Only show the inputs badge when num_inputs is non-zero, since
'0 inputs' is redundant information.

templates/index.html

@@ -282,7 +282,7 @@ function renderProblems(problems) {
             </div>
             <div class="problem-card-body">
                 <span class="badge ${badgeClass(problem.source)}">${problem.source}</span>
-                <span class="badge badge-info">${problem.num_inputs} inputs</span>
+                ${problem.num_inputs ? `<span class="badge badge-info">${problem.num_inputs} inputs</span>` : ''}
             </div>
             <div class="problem-card-info">
                 <span>Index: ${problem.idx}</span>