title: What this error is invalid context 0x0?
body: <p>I wrote the following code in ViewDidLoad</p>
  
  <pre><code>// Implement viewDidLoad to do additional setup after loading the view, typically     from      a nib.
       -(void)viewDidLoad {
      [super viewDidLoad];
  
  NSString *str = [NSString stringWithFormat:@"Veer"];
  
  CGColorSpaceRef rgbColorspace = CGColorSpaceCreateDeviceRGB();
  CGFloat values[4] = {55.0, 0.0, 0.0, 1.0}; 
  CGColorRef glowColor = CGColorCreate(rgbColorspace, values); 
  CGContextRef context = UIGraphicsGetCurrentContext();
  CGContextSetShadowWithColor( context, CGSizeMake( 5.0, 0.0 ), 20.0f, glowColor);   
  [str drawAtPoint:CGPointMake(10.5f, 0.5f) withFont:[UIFont      fontWithName:@"Helvetica" size:100.0f]];    
  UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(60, 200, 250, 100)];
  [label setBackgroundColor:[UIColor clearColor]];
  label.font=[UIFont fontWithName:@"DBLCDTempBlack" size:50.0];
  label.textColor = [UIColor colorWithRed:0.0 green:1.0 blue:0.0 alpha:1.0];
  [label setText:str];
  
  [self.view addSubview:label];
    }
  </code></pre>
  
  <p>In Console I saw as </p>
  
  <pre><code> Testing Clock[3286] &lt;Error&gt;: CGContextSetStyle: invalid context 0x0
   Testing Clock[3286] &lt;Error&gt;: CGContextSetFont: invalid context 0x0
   Testing Clock[3286] &lt;Error&gt;: CGContextSetTextMatrix: invalid context 0x0
   Testing Clock[3286] &lt;Error&gt;: CGContextSetFontSize: invalid context 0x0
   Testing Clock[3286] &lt;Error&gt;: CGContextSetTextPosition: invalid context 0x0
   Testing Clock[3286] &lt;Error&gt;: CGContextShowGlyphsWithAdvances: invalid context 0x0
  </code></pre>