style: handle empty input array in FindMin.findMin (#4205)

* tests: add test case with mininum not being at the beginning

* style: throw IllegalArgumentException when input is empty

* style: use enhanced for loop

* docs: update doc-str

src/test/java/com/thealgorithms/maths/FindMinTest.java

@@ -1,6 +1,7 @@
 package com.thealgorithms.maths;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
 
@@ -23,4 +24,17 @@ public class FindMinTest {
     public void test2() {
         assertEquals(0, FindMin.findMin(new int[] { 0, 192, 384, 576 }));
     }
+
+    @Test
+    public void test3() {
+        assertEquals(0, FindMin.findMin(new int[] { 10, 10, 0, 10 }));
+    }
+
+    @Test
+    public void testFindMinThrowsExceptionForEmptyInput() {
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> FindMin.findMin(new int[]{})
+        );
+    }
 }