When I start my forge, my game crashes while its Initializing Minecraft Engine. This is the report file:

---- Minecraft Crash Report ----
// You should try our sister game, Minceraft!

Time: 11/24/17 10:35 PM
Description: Initializing game

net.minecraft.client.renderer.StitcherException: Unable to fit: missingno - size: 16x16 - Maybe try a lowerresolution resourcepack?
    at net.minecraft.client.renderer.texture.Stitcher.func_94305_f(Stitcher.java:72)
    at net.minecraft.client.renderer.texture.TextureMap.func_110571_b(TextureMap.java:258)
    at net.minecraft.client.renderer.texture.TextureMap.func_174943_a(TextureMap.java:94)
    at net.minecraftforge.client.model.ModelLoader.func_177570_a(ModelLoader.java:129)
    at net.minecraft.client.resources.model.ModelManager.func_110549_a(ModelManager.java:28)
    at net.minecraft.client.resources.SimpleReloadableResourceManager.func_110542_a(SimpleReloadableResourceManager.java:120)
    at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:478)
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:329)
    at net.minecraft.client.main.Main.main(SourceFile:124)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
    at net.minecraft.client.renderer.texture.Stitcher.func_94305_f(Stitcher.java:72)
    at net.minecraft.client.renderer.texture.TextureMap.func_110571_b(TextureMap.java:258)
    at net.minecraft.client.renderer.texture.TextureMap.func_174943_a(TextureMap.java:94)
    at net.minecraftforge.client.model.ModelLoader.func_177570_a(ModelLoader.java:129)
    at net.minecraft.client.resources.model.ModelManager.func_110549_a(ModelManager.java:28)
    at net.minecraft.client.resources.SimpleReloadableResourceManager.func_110542_a(SimpleReloadableResourceManager.java:120)
    at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:478)

-- Initialization --
Details:
Stacktrace:
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:329)
    at net.minecraft.client.main.Main.main(SourceFile:124)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
    Minecraft Version: 1.8.9
    Operating System: Windows Vista (x86) version 6.0
    Java Version: 1.8.0_25, Oracle Corporation
    Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
    Memory: 108526536 bytes (103 MB) / 273580032 bytes (260 MB) up to 523501568 bytes (499 MB)
    JVM Flags: 6 total; -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    FML: MCP 9.19 Powered by Forge 11.15.1.1722 3 mods loaded, 3 mods active
    States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
    UCH    mcp{9.19} [Minecraft Coder Pack] (minecraft.jar) 
    UCH    FML{8.0.99.99} [Forge Mod Loader] (forge-1.8.9-11.15.1.1722.jar) 
    UCH    Forge{11.15.1.1722} [Minecraft Forge] (forge-1.8.9-11.15.1.1722.jar) 
    Loaded coremods (and transformers): 
    GL info: ' Vendor: 'Intel' Version: '1.4.0 - Build 7.14.10.1409' Renderer: 'Intel Bear Lake B'
    Launched Version: 1.8.9-forge1.8.9-11.15.1.1722
    LWJGL: 2.9.4
    OpenGL: Intel Bear Lake B GL version 1.4.0 - Build 7.14.10.1409, Intel
    GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Not using framebuffer objects because OpenGL 1.4 is not supported, EXT_blend_func_separate is supported, OpenGL 3.0 is not supported, ARB_framebuffer_object is not supported, and EXT_framebuffer_object is not supported.
Shaders are not available because OpenGL 2.1 is not supported, ARB_shader_objects is not supported, ARB_vertex_shader is not supported, and ARB_fragment_shader is not supported.
VBOs are available because ARB_vertex_buffer_object is supported.

    Using VBOs: No
    Is Modded: Definitely; Client brand changed to 'fml,forge'
    Type: Client (map_client.txt)
    Resource Packs: 
    Current Language: English (US)
    Profiler Position: N/A (disabled)
    CPU: 2x Pentium(R) Dual-Core CPU E5200 @ 2.50GHz

 

Thank you for helping!

First, I would try to update away from 1.8.9, it's getting pretty old and will probably stop being supported here much as 1.7.10 has.

Quote

net.minecraft.client.renderer.StitcherException: Unable to fit: missingno - size: 16x16 - Maybe try a lowerresolution resourcepack?

Are you using a texture or resource pack of some kind? If so, I would try just using the standard minecraft graphics and see what happens.