Added info about guard blocks

CONTRIBUTING.md

@@ -143,8 +143,17 @@ Try to stay inline with the code that surrounds you, having an entire package or
 * Packages must be all lowercase, consecutive words should generally be avoided. (e.g. `io.github.thebusybiscuit.slimefun4.core.something`)
 #### 7. Style preferences
 * Use **Spaces**, not Tabs!
-* Try to keep ternary operators to a minimum, only in return statements (e.g. avoid doing this: `int y = x == null ? 1: 2`)
-* if/else statements should always include a bracket, please avoid one-line statements (e.g. Avoid doing: `if (x == 0) return;`)
+* Try to keep ternary operators to a minimum, only in return statements. (e.g. avoid doing this: `int y = x == null ? 1: 2`)
+* Try to keep so-called "guard blocks" to a minimum. One guard block is fine but having multiple guard blocks before getting to the actual code... Well, you might wanna refactor your code there. Example:
+```java
+// guard block
+if (something) {
+  return;
+}
+
+// Actual code...
+```
+* if/else statements should always include a bracket, please avoid one-line statements. (e.g. Avoid doing: `if (x == 0) return;`)
 * We do not enforce any particular width or column limit, but try to prevent your lines from becoming too long.
 * Annotations for methods or fields should never go on the same line, place them on the line above.
 * Comments should never go on the same line as code! Always above or below.
@@ -156,7 +165,7 @@ Try to stay inline with the code that surrounds you, having an entire package or
   * In variable assignments: `int x = 123;`
   * In a for-loop: `for (int i = 0; i < 10; i++) {`
   * Before and after statement parenthesis: `if (x != null) {`
-  * Inbetween array initializers: `int[] array = { 1, 2, 3 };
+  * Inbetween array initializers: `int[] array = { 1, 2, 3 };`
   * After the double slash of a comment: `// This is a comment`
 * Slimefun follows the **1TBS / OTBS** Bracket-Style standard (One true brace style):
 ```java