Fix potential crashes from bad block/item definitions for images. Fix wrapped whitespace not being trimmed.

src/main/resources/assets/opencomputers/doc/en_US/drone.md

@@ -0,0 +1,5 @@
+# Drone
+
+![Big brother is trying to watch you.](oredict:oc:drone)
+
+Drones are built using a [drone case](droneCase1.md) in the [assembler](assembler.md). They are entity-based [robots](robot.md), a little cheaper but with more limited functionality. 

src/main/resources/assets/opencomputers/doc/en_US/robot.md

@@ -0,0 +1,7 @@
+# Robot
+
+![His name was Tobor.](block:OpenComputers:robot)
+
+Unlike computers, robots can move around and interact with the world much like a player can. They can *not* interact with external components, however! If you need to communicate with a computer or other robots, use a [wireless network card](wlanCard.md), or create some low-level protocol using redstone signals via a [redstone card](redstoneCard1.md), for example.
+
+Robots are built by placing a [computer case](case1.md) in an [assembler](assembler.md).

src/main/resources/assets/opencomputers/doc/en_US/tablet.md

@@ -0,0 +1,9 @@
+# Tablet
+
+![Touch me if you can.](oredict:oc:tablet)
+
+ Tablets are built by placing a [tablet case](tabletCase1.md) into an [assembler](assembler.md), configuring as desired and assembling it. Tablets act as portable computers that cannot directly interact with the world - for example, basic [redstone cards](redstoneCard1.md) do not work in them. A number of upgrades, however, do, such as the [sign upgrade](signUpgrade.md) or the [piston upgrade](pistonUpgrade.md).
+
+To force rebooting a tablet, shift-rightclick it while holding it in your hand. Unlike computers, tablets do not persist across the player holding it leaving and re-entering the game. They also do not persist across the player holding the tablet changing dimensions (e.g. going to the Nether or back).
+
+Tablets can be put into a [charger](charger.md) to refill their energy, and to access the first [hard disk](hdd1.md) built into the tablet from a [computer](case1.md) connected to the charger - in this setup, the charger will act similar to a [disk drive](diskDrive.md), with the tablet being the [floppy disk](floppy.md). This can be very useful in case you forgot to install an OS on the hard drive built into the tablet, or after bricking a tablet's OS.

src/main/scala/li/cil/oc/util/PseudoMarkdown.scala

@@ -175,10 +175,11 @@ object PseudoMarkdown {
     override def height(indent: Int, maxWidth: Int, renderer: FontRenderer): Int = {
       var lines = 0
       var chars = text
+      if (indent == 0) chars = chars.dropWhile(_.isWhitespace)
       var lineChars = maxChars(chars, maxWidth - indent, renderer)
       while (chars.length > lineChars) {
         lines += 1
-        chars = chars.drop(lineChars)
+        chars = chars.drop(lineChars).dropWhile(_.isWhitespace)
         lineChars = maxChars(chars, maxWidth, renderer)
       }
       (lines * lineHeight(renderer) * resolvedScale).toInt
@@ -187,9 +188,10 @@ object PseudoMarkdown {
     override def width(indent: Int, maxWidth: Int, renderer: FontRenderer): Int = {
       var currentX = indent
       var chars = text
+      if (indent == 0) chars = chars.dropWhile(_.isWhitespace)
       var lineChars = maxChars(chars, maxWidth - indent, renderer)
       while (chars.length > lineChars) {
-        chars = chars.drop(lineChars)
+        chars = chars.drop(lineChars).dropWhile(_.isWhitespace)
         lineChars = maxChars(chars, maxWidth, renderer)
         currentX = 0
       }
@@ -201,6 +203,7 @@ object PseudoMarkdown {
       var currentX = x + indent
       var currentY = y
       var chars = text
+      if (indent == 0) chars = chars.dropWhile(_.isWhitespace)
       var numChars = maxChars(chars, maxWidth - indent, renderer)
       val interactive = findInteractive()
       var hovered: Option[InteractiveSegment] = None
@@ -215,7 +218,7 @@ object PseudoMarkdown {
         GL11.glPopMatrix()
         currentX = x
         currentY += (lineHeight(renderer) * fontScale).toInt
-        chars = chars.drop(numChars)
+        chars = chars.drop(numChars).dropWhile(_.isWhitespace)
         numChars = maxChars(chars, maxWidth, renderer)
       }
 
@@ -489,7 +492,8 @@ object PseudoMarkdown {
       val href = m.group(2)
       if (href.startsWith("item:")) {
         val desc = href.stripPrefix("item:")
-        val (name, optMeta) = desc.splitAt(desc.lastIndexOf('@'))
+        val splitIndex = desc.lastIndexOf('@')
+        val (name, optMeta) = if (splitIndex > 0) desc.splitAt(splitIndex) else (desc, "")
         val meta = if (Strings.isNullOrEmpty(optMeta)) 0 else Integer.parseInt(optMeta.drop(1))
         Item.itemRegistry.getObject(name) match {
           case item: Item => new ItemStackSegment(s, m.group(1), Array(new ItemStack(item, 1, meta)))
@@ -498,10 +502,11 @@ object PseudoMarkdown {
       }
       else if (href.startsWith("block:")) {
         val desc = href.stripPrefix("block:")
-        val (name, optMeta) = desc.splitAt(desc.lastIndexOf('@'))
+        val splitIndex = desc.lastIndexOf('@')
+        val (name, optMeta) = if (splitIndex > 0) desc.splitAt(splitIndex) else (desc, "")
         val meta = if (Strings.isNullOrEmpty(optMeta)) 0 else Integer.parseInt(optMeta.drop(1))
         Block.blockRegistry.getObject(name) match {
-          case block: Block => new ItemStackSegment(s, m.group(1), Array(new ItemStack(block, 1, meta)))
+          case block: Block if Item.getItemFromBlock(block) != null => new ItemStackSegment(s, m.group(1), Array(new ItemStack(block, 1, meta)))
           case _ => new TextSegment(s, "Failed resolving " + href)
         }
       }